Why do women in bars get turned off by guys who ask broad questions?

That's a tough one..I'm sorry, but seeing as I'm a woman myself..it's hard to give advice for this. However, maybe try first complimenting the woman before asking something. Maybe say something like "Hi, you look very lovely this evening. I've noticed you here before, and I wonder if you'd like to chat?" Try to not sound like a creeper while saying this btw ;) Rephrase however you wish. And just go from there I suppose. Also, keep in mind you might just be going to a really sucky bar. Maybe try a few different ones, or try online dating. Best of luck! :)