Its there desire to open it to a ESport that drives the similar underlying main objective of the sPVP. They want the fundamentals to remain the same like in any sport while changing up the venue a bit with secondary objectives. IF that doesnt float your boat thats why there is WvWvW, which is extremely well done and arguably offers a variety of ways to experience and play it.My main gripe with GW2's pvp is how little there is to do. WvW, rated AB, and AB. That's it. I really would had liked that the 3 different battlegrounds had different objectives each, but giving the exact same goal to all 3 is pretty boring. I really hope they add other objectives in the future.
In regards to the "amount" of spvp battle grounds per say its on par with most if not all games at release. It will be expanded on. You cant go into it expecting 10 different maps each with unique this and thats out of the box. How they play however is a design choice by them to keep them easy to pick up and learn.