That's too many words and also implies you have that much of a choice over who you talk to when you're new. Some places are meant to be more social than others. Emphasis is on "nice neighborhood bar", i.e. not a dive full of shady sour-faced dudes who whine about drink prices, don't tip, and are looking to "score" or whatever. Doesn't have to be fancy, just not the college crowd.

The default move for pretty much anyone new is to find an open seat at the bar near people who are also there alone (you know because they're sitting apart). Order a drink and try to guess simple questions or comments they might also have in mind. Try to keep it lighthearted. In fact the more restrained you are the more some of those people are going to be weirded out by you. You're expected to be comfortable. They want you to say something. The best way to avoid the extra words is to say things when you're also doing something else. If you are ordering a drink next to them, they're already listening and watching you. If you turn to them to say anything in that moment you didn't need to break any ice.

Everyone likes answering questions about themselves because they're there to be seen as much as you. Notice something and be nice. 90% of the time even just "nice shoes..." will get a smile and an in. "Where did you get them?" Next part depends on the shoes: "What do you do? Do you run? Do you hike? Did you just get out of work (non-slip/uniform)? Did you just come back from a wedding? Do you make balloon animals? (kidding)" "What are you drinking? Nice choice. Have you visited that brewery down the road? You watch football? Have you had the food here? Why don't they ever put enough salt? Can you pass the salt? Hey what's the bartender's name? Melissa! Can I get some silverware and salt? Thanks so much, oh and a shot for my friend." etc.

The hardest part is the first friends, but they also determine what other people you'll meet. Don't overthink it if it seems everyone's the same. Just pick the person you were most interested in first because if you don't then people will still assume that's why you're near them instead.

EDIT: I can't believe I glossed over your question, but...

> What’s in it for them for telling you.

What's in it for them is the same as what's in it for you. You want to relax somewhere and meet new people. For some people there's not much in it for them other than being a friend to someone who needs it. For yet still others, they simply don't ask such questions because they think the mindset of needing to always make a return sounds like work, and they're not there to work.