Based on the developers we've talked to, DRM generally isn't the limiting reason. The default DRM added to Steam is easily cracked from what I'm aware of, and once your game is cracked there's no much you can do to prevent illegal distribution. DRM makes it harder for legitimate players to run your game, and generally doesn't stop pirates. There are other DRM free sites that do quite well which backs up this observation.
I think part of the reason why people remove their game after they've run a beta is that they want to consolidate how they distribute their game. Each new platform they distribute on is a slight overhead in terms of keeping things updated. Many developers don't have the extra resources to maintain pages on alternative platforms. We're trying to combat this by making things as easy as possible.