What does "should" mean? If I say "you should really get that cut checked out, it looks infected", then I'm making a recommendation to you or giving you advice

What does "should" mean? If I say "you should really get that cut checked out, it looks infected", then I'm making a recommendation to you or giving you advice (solicited or not). But here you seem to be giving advice to a class of jobs, which doesn't make a lot of sense. A class of jobs has no agency. Are you advising plumbers (one example of a blue collar job) to charge more for their services? I'm sure the thought occurred to them and it doesn't work for one reason or another. Are you advising customers of the plumber to pay more? Have you ever requested plumber services, and if so, did you pay the plumber "much more" (in other words, are you taking your own advice)?