[bpostal]

It's the EULA you 'signed' when you joined the game. Don't feel bad, I didn't really read it either. That's the legal reason.
For certs it's a bit different. From what I remember their reasoning for a lack of recert option (that Planetside had) is that you will always continue to earn certs. You won't ever be capped out and thus it's not a problem.
Try to cert/buy items that play to your playstyle instead of what looks good/OP.