I do my level best to treat everyone with respect and be genuine and polite and all that. I do it because that's just how I am, I don't expect anything for it. And, no, I don't always get it right. I'm human and perfectly capable of making an arse of myself, sticking both feet in my mouth and all that. And I have had plenty of experiences that fit with the saying "No good deed goes unpunished". But I also have found that people in service industries and the like will be wonderful to me because I treat them like a human being instead of a doormat to wipe my feet on. (People in positions of power seem to divide up between those who are offended that I don't grovel and kowtow and those that are charmed.)
Some actual experiences of mine:
Long line at a crowded mall food court eatery. I'm a regular and I tend to order the same thing most of the time. My order is ready and waiting for me by the time I get to the cash register. I walk off to find a table and eat while other people who ordered and paid ahead of me (and still don't have their food) stand there with their mouth's hanging open, fuming and apparently wondering "who the fuck is she???!!!"
Long line at an eatery. I am brought the cappuccino I typically order with lunch well before I get to the cash register. While other people stand around looking at me funny, I sip my cappuccino and guiltily wonder if the person who brought it to me might get in trouble.
Last few minutes before the place is closing early on a holiday and I slip in to get something to go. They toss in a free cup of their new soup for me to try.
I have also been given free sodas, discounts on my meal, had sides/other extras tossed in for free, and have been given a stack of promotional coupons when other people are being given one coupon with their order. At the grocery store I frequent, it is common for someone to open an extra register basically just for me, so I won't have to stand in line.
If you are genuinely nice and respectful to people who routinely get crapped on, there are tangible benefits. I don't recommend you do this with some expectation of tangible benefits. I think people can smell it when they are basically being used in that way -- it might pay off initially, but will likely come back to bite you later if you are just being a smarmy manipulative charmer. But if you are genuine, yes, this does tend to pay off -- though it doesn't magically protect you from people randomly being asses to you or some such. Some people seem to behave more badly towards me because I sometimes wind up with a reputation for nice, polite behavior. They seem to be either jealous or trying to provoke a reaction to prove I'm not that nice ....or something. So it's not all upside. Still, I find the benefits I do get out of it are pretty valuable to me. It seems to routinely pay off the most under the worst circumstances, when I most need a little something extra. For me, this is frequently a saving grace in a life that can be pretty tough.