I'm brand new but this is my perspective as a potential wholesaler (and businesswoman). I believe that it's semantics at play, with all business, and of course perspective. No one, not even a social worker (what I went to school for :-) unless they are literally volunteering is doing a free service. So maybe I'm naive, but I would give sellers more credit than assuming that they do not realize that some random person coming to them (whether calling themselves a wholesaler, investor, or cash buyer) doesn't stand to make a profit.
It's obviously a transaction. But just because there's a transaction involved doesn't mean it isn't also a service. No different than a trash man, a painter, an agent and yes, even a wholesaler. From my understanding, if done right, a wholesaler is seeking people that are "motivated" (aka quite distressed or in a hurry to sell for whatever reason). It's clear that they're not getting market value for their house, and in return they also don't have to worry about commissions, repairs, or a lengthy process.
For some people in certain situations this is a relief. For others (like my parents, who were approached years ago) it isn't worth it after all they've put into the house.
Personally, I don't care about using the word service, I probably won't actually, but I think it is still a service at the end of the day for people that need it. To some agents have a bad rap, wholesalers, etc. It's all perspective, and at the end of the day most are selling something (even their brand)-"service" or not.