Why are so many people against lab-grown meat?

I've never understood the problem people have with lab-grown meat (apart from those selling the traditional type).

I like meat, but I don't like killing animals and I find factory farming horrific. So it's a win-win. It's a lot less "icky" than thinking about what factory farm animals suffer.

I know it's expensive at the moment, but once it's on a par with "traditional" meat, what's the problem?