If I had a PC problem, I posted here and was helped free of charge it would also be good for me. Same as going into a shop and getting some free help.
If people see that someone is helpful and that gives them some business - fine.

If someone is spamming, they could be reported to the mods and get them deleted/banned.

If a little extra business maybe encourages them to help more, fine, it also helps us more.

I would rather be helped by someone, even if they have a commercial interest than not helped at all. At least with them being identified I know where I am.