I've been calling this one out for awhile now: The game currently gives absolutely no reward for leaving your base - to the contrary, it encourages staying nearby.
Take out the Maller B (I think B) sometime when all but two of your ten weapon systems are ammo-based and you have no extra tonnage. Why in god's name, given the hideously slow speed of the thing, would you EVER get far from your re-arm point? Thankfully, the APC has solved that problem, but if we want to brawl with one of those things (or have a decent midfield fight) we can look forward to a two minute walk back, and a two minute walk to the lines again.
...or I can sit in the base, make you come to me, and repair swiftly after each fight. Maybe even DURING each fight if I'm lucky enough.
People base-poptarting can be called lame, or they can be called "using the current game mechanics." There are a few ways we could fix that situation:
1- Dramatically slash cbill *AND* rank gain for kills within X radius of the base.
2- NOT REPEAT NOT ADD IN LONG TOM DEFENSE SYSTEMS AROUND BASES. (Seriously. This is a terrible idea. You're basically GIVING them a "stationary and safe" zone from the weapon designed to make standing in a base NOT SAFE.)
3. See above, change the wording to "missile."
4. Create a "dampening field" around bases that causes all weapons not to fire until someone is physically clear of the base's dimensions - for safety's sake, there's a lot of expensive equipment in here, right? - and have it automatically turn off if someone hostile comes within X radius of the base.
5. Have base systems "overload" and turn off if too many players are in there, stopping all repair and rearm actions. Too many players varying from server to server, and probably suspending this rule for the first five minutes or so.
6. Have a much slower, much more expensive version of the APC that can also repair.
7. Put objectives on the map that, if held for a significant period of time, give player a significant cbill and/or rank bonus. (Possibly double gain for a time equal to how long you held the structure after you leave it and while you're actually at it?)
Right now, people have no reason to leave bases and indeed it's tactically foolish to do so. (It'll become tactically idiotic to do so if they put in Long Tom base defenses.) Until there are valid tactical or strategic reasons to do so, this trend will continue.