There's lots on this from previous discussions, including replies from the Devs. I guess you could search for it in the old threads. I remember crying out for the switch to blow function at one point. But I think it would kill the game in many scenarios (Piper's Race, if you're Axis, being one, I think), at least as they are presently balanced. That said, it does seem unrealistic - regardless of doctrine - to not be able to pre-emptively blow bridges. It did happen, after all, during the war (regardless of strict doctrine)that bridges were dropped long before any contact, as part of a plan. Think how many bridges the allies dropped (by air) leading into D-day, for example. Myself, I'm happy with the way it's modelled now, for game play reasons. I want to be able to race Piper over Trois ponts, if possible. That wouldn't happen if you had the switch, because who is going to play Piper's Race as allies and not drop every single primed bridge (bar the northernmost, perhaps) in the first few minutes of the game. And that didn't happen historically.
Doctrine drives how a military force develops and procures combat weapons and equipment; defines unit organizations and command hierarchy; establishes the lines of communication among peer organizations and within the command hierarchy; defines soldier skill requirements for those organizations; recruits soldiers to meet those skills requirements; and trains soldiers / organizations on using weapons, running the organization, and developing troop readiness for any assigned (by doctrine) operations.
Within real military organizations, ignoring doctrine can lead to court martial, imprisonment, and execution depending on the harm done.
Doctrine does allow for cutting lines of communication among enemy organization and constraining a foe's ability to maneuver.
The issue with Command Ops is whether the scenario designer's plan implemented at the time the battle included preparations for extreme denial of maneuver operations before enemy contact (which leads to the scenario designer designating a number of bridges primed for destruction on short notice and / or showing normal crossings closed to use) or requires the use the deny crossing maneuver to accomplish the mission within the scenario timeframe.
Much like the issue of bombardment effects on armored formations, there may be some room to look into modelling bombardment or even air strikes as a means to take out bridges on an ad hoc basis. My guess is even if bombardment / air strikes are options for destroying bridges, the probability of hitting a structure of a specific design effectively enough to destroy it as a minimum would take as much game time as defined to prime those same structures with appropriate deny crossing resources. Does save the commander from having to use ground resources to prime a bridge, but doesn't implement the destruction of the crossing any more quickly in the long run.
But given the relative importance of other enhancements already planned for the game engine to model expanded combat operations or force confrontations (minefields, water borne combat maneuver, Russian operational doctrine, etc.), I'd say the priority for even more opportunities to blow bridges on command is low.