Various observations/thoughts-
In the military, the progression through junior and NCO ranks (I will use the latter term generally, and yes in Canada that would include our Warrant Officers) will generally start with an apprenticeship through to mastery of the job at the individual technicl level, and then up to command of small teams whose success is very dependent on a high level of technical expertise by the commander. The span of control of a section or crew commander and what they are responsible for necessitates years and years of experience at a very granular level.
As one goes up the chain of command in an army unit, the nature of the needed expertise begins to change. A platoon commander is an apprentice in his or her own right- they need less of the nitty gritty expertise because they have their NCOs for that. The time of the commanders at platoon, company, and battalion level, however, is much too valuable to spend on housekeeping, and the care and feeding of troops, and so they depend on those very experienced NCOs to take care of that for them.
The span of control of military officers can grow so large by late in a career (brigade, divisional commanders and such) that they really do need to have spend some time getting good at each of thsoe command levels, plus the various time in staff and other roles, as well as furthering their professional education. At each level they have to have some solid grasp of the conduct of operations a couple levels down from their own- the company commander will need to know how his weapons dets are best employed, and how his sections can be best used, though generally that will be them being grouped within their platoons The battle group or brigade group commanders have to really know how to use their companies, but needn't really concern themselves down to where individual platoons are placed. They have bigger stuff to worry about.
I would contend that few people will succeed in becoming senior NCOs, and then still have enough time left in their careers to be senior officers in command roles. To get those really skilled very senior officers, they have to get as much out of them as possible in the roles officers conventionally fill, knowing that in their officer apprenticeship they will be under the eye of and mentored by both more experienced company commander,s and their platoon 2ics, and so they can be dropped right into that initial command level without spending years mastering individual soldier skills and tecnical/equipment matters to the level that their experienced NCOs will.
So- I think in large part the divergence right from or almost from the start in noncommissioned and commissioned officer ranks in the military is largely necessity.
In the policing world it's pretty different. For one, simply put the police universe doesn't have large battles to be fought. Commissioned officers are generally senior managers, oversight, and administrators. An inspector in an RCMP detachment for instance may command the detachment, but that 'command' still generally involves delegating operational day to day policing matters to a Sergeant or Staff Sergeant who will be called an Operations NCO. You will usually only see a commissioned officer take a direct command role with tactical decision making if they are commanding a critical incident, as a trained incident commander- a SWAT call, hostage taking, barricaded subject, etc- or if they are at a higher level commanding a major event.
In policing the degree of individual responsibility for things with significant consequence goes right down to the individual police officer level. Any police officer can be potentially making decisions that have considerable import on the safety and freedom of individuals. They have to have technical expertise of their own (application of the law, knowledge of their powers and authorities, knowledge of the actual physical techniques of police interventions, knowledge of a whole ton of policy) that in the military will usually be seen at section command level at lowest. That's not to say a rookie cop has the same responsibility as an infantry section commander there's no easy analogy that immediately comes to mind- but there is potential *consequence* down to a low level.
With same, the oversight requirements from police officers necessitate those commissioned officers to have considerable technical knowledge to fall back on. The individual commissioned police officer is likely to be in a role where they are responsible for the safety of a whole community, either for a given shift or as 'the boss' 24/7. The RCMP inspector commanding the detachment in Fort Moose's Armpit, Manitoba, may command a group of police the size of a platoon- but he'll also be the effective chief of police for a community of tens of thousands, responsible for a detachment budget in the millions, responsible for liaising with community leaders, legal experts, politicians, etc etc. A newly commissioned police officer in the civilian world *cannot* be an apprentice the way a subaltern is. On the flip side, even the largst police force in Canada, the RCMP, has only six commissioned officer ranks- a member must be at least a corporal first, which in turn almost always means at least eight years of service. Sergeant or Staff Sergeant is more common.
While there are some overlaps in military and police rank structures, there are many differences too... Experienced, senior constables may carry considerable responsibility. A police Corporal or Sergeant may fill jobs that in the military would never go to someone who isn't a commissioned officer. Police organizations also much less employ very senior NCOs in roles akin to Sergeants Major- they certainly do not fill 'command team' roles in a way akin to a military command team, although there will be some analogous duties.
Neither system is perfect. Both suit their particular context. There is certainly some value in some time spent in the ranks before commissioning in the military, but I think there's a quickly diminishing rate of return on that, and the longer one stays noncommissioned before commissioning,t he larger the opportunity cost to a subsequent commissioned officer career.