What doesn't make sense is having an INFINITE box that everyone can fill up on. I love splash damage's approach to ammo resupply in brink. In BC2 it works fine but I find the distribution in Brink to be much more intuitive.
In previous SD games, ammo (and health) didn't work exactly like it does in BC2. In their games, kits were consumed by players rather than acting like a mini supply depot, so if you dropped a kit, the player than ran over it would get supplied (not to full capacity) and the kit would disappear. This could prove really inefficient, since players could run off without grabbing a kit or another player could pick up instead. Also, really low ammo or health players could require a lot of kits to fill them up (and a lot of energy bar) - this was alleviated by actual supply crates on maps, that housed a finite supply of ammo and medkits that players could stock up on (on either team.) Also, playing a Medic, there was a tactic known as a"TK revive," that had mixed reactions among the community.
It took 4 medkits to fill up a players health, yet revived players came back with 50% health. A TK revive was a tactic used (usually by more "seasoned" medics) were Medics would deliberately kill a teammate who had really low health, then revive him (to 50% health) and then only need 2 kits to top him off, rather than throwing 4 kits total. With Brink, medkits (not sure about ammo) heal for 100% and they are delivered directly to the player that needs them. Add in the new revive system, and the ability to pick and choose skills and weapons freely, and Medics seem much more effective and approachable to players.
I remember the first time I played BC2 and dropped a medkit - I was like "why isn't it disappearing?" lol.