I don't get a lot of it, I don't tend to get patronised by tradespeople or salespeople, most of the ones I've come into contact with have learned not to do that I suspect.
I do get it a bit though being a SAHM - its assumed I am being "supported" by my husband. This happens more online than anywhere, if I take part in a debate about work/life balance or division of household jobs etc and thus far women have been the worst though to be fair the forums I frequent tend to have more women than men or certainly in these discussions it tends to be that more women contribute.
It was once suggested to me during a discussion about work life balance that my husband would be able to spend more time at home if I went out and got a job, and then he could work less. I know that for some, in theory, that is the case but FFS my husband doesn't do the job he does because we need X amount of money - he has a career that to enjoy and progress he has to put in a certain amount of effort. This was the case for me too when I was pursuing my previous career. If I were to return to work, it would make it even less possible for him to progress his career due to the children we had together.
If he wanted to give work up, he could. (not forever but he could take a sabbatical no problem) I have an independent income which I would be most happy for him to "live off" or "be supported by" or whatever. He doesn't want to, and I don't want him to because I know what he gets from his work, and its important to me that he is happy too.
It is often implied that my husband is doing me some huge favour because I don't have to work, as if its all down to him, and that I should be in some way obliged to make it up to him by doing all the housework or giving him blowjobs or some such.
Yet it is never implied I'm doing him a huge favour having a career break to help raise the 2 children we had together - its just assumed that that would happen and that I'd be grateful for the opportunity. I don't think I'm doing him personally a favour as such - we both do favours for the family as a whole of various kinds.
I think it grates my father-in-law big style that the bigger, faster, main family car is "mine" - registered in my name, etc, and driven mainly by me - and the small, much cheaper to buy and run and much less fun car is "his" - it only gets driven to the train station and back once a day, so no need for him to have anything too fun at the mo whereas I do more schlepping about with kids and then we use it as the main vehicle on the weekend. He still likes to say its DH's car which he lends me, oh its nice of him to "let" you drive it during the week, I suppose it does make sense as he doesn't do much driving etc etc 
To be fair I don't tend to go into massive detail about our personal set of circumstances and motivations for setting up things the way we do but it is still interesting/irritating to see what the default assumptions are.