columbus, this is a game in which everyone can do anything they want. Capture bases, defend bases, furball, GV, etc. I guess it's too bad not everybody flocks to defend a base, or attack a base, or help a friendly in trouble...but that's what makes this more fun than playing a single-player offline game - there are real people out there. Just try to accept that, and have fun however you want.
It's a combat game, so if you get to see combat count yourself lucky and know that neither you nor anyone else really dies, and hopefully you log off happy with the fights you got into.
Creating more arenas or more "you can only do this here" arenas will do nothing but create more animosity and result in fewer players in the same arena, which spells less fun for everyone. In the end, it's HTC's business to keep the most people happy that they can, and only they know and can decide how to best achieve that while maintaining a profitable company.