the nature of map doesn't allow it; that's the point (at least in 3v3+). at least for caches on normal territory points right outside the bases.
I don't disagree there, but that's again an issue of map design and the inherent flaws in the game mode than it is with the balance of cache bonuses. 1v1 and 2v2 do not have this issue, and are the game is balanced around them first and foremost. The biggest problem with caches is that too many maps give you an easily defend strat point next to your base (that isn't a cutoff), which makes them pretty risk free to build. The gold standard for map design is something like Koholodny where the point is far enough away from your base that it can still be killed, but also quite defensible.
3v3/4v4 is also a game mode where you have to start looking at each player as a component of army strength. In 1v1 and 2v2 you may send 1-2 units off on their own to do stuff, but in bigger game modes you are much better served by acting like a company in a real war wherein you move all your stuff cohesively and work with your teammates as separate forces. The fun of 3v3/4v4 imo is when you have a good team you can strike multiple places at once with efficacy, and use teamwork to set up ambushes etc.
EDIT:
I think the simplest solution would be to have fewer strat points in 3v3/4v4 maps. This would naturally slow down income and make capping/controlling points more significant.