I wouldn't say nobody wants Pristine realms. I would say many people want Legacy Servers and Pristine realms isn't an answer to that problem.
Pristine Realms could work on their own, as a way to return some of the challenge to low-level gameplay in WoW and hopefully return some of the community aspects that many have been craving for. Legacy Server discussion has so many facets to it that it's difficult to talk about because everyone has their own idea of what they should be, and their reasons for playing it. Some people just want a harder version of WoW, some people prefer the gameplay of the classic talent system, some people want to play simply for nostalgia, etc.
Spending resources to polish up Legacy servers into Blizz-quality playable form is definitely a step in the wrong direction for Blizzard (as a company). It's what many players want to see, but we'll see in time how successful they really will be. The onus is on Blizzard once they set the ball rolling. Whether or not people play on Legacy Servers will be their responsibility, and the community will be quick to blame any shortcomings for anything potentially negative that happens.
This situation isn't easy to predict, but it's certainly a big investment for Blizzard to take from a business standpoint.