[maxk42]

I fail to understand how you equate "Go on interviews even when you don't need a job." with "waste people's time." The idea is to interview when you don't need a job so that you can easily negotiate for the best possible offer. If they won't beat your current compensation or benefits you can say "thanks but no thanks" and if they can you can say "I'd be delighted!" Nobody's time is wasted - the hiring company just has a higher bar to meet to entice you to join their team. If anyone's time is wasted it's yours when they can neither make a competitive offer nor help you to improve your skills in the interview.

If you've only ever interviewed when you were desperate to take the first job that comes along then you're almost certainly under-compensated. Anyone who's not taking a better job when they get the chance is leaving money on the table.