They are also the most competent and qualified to make that determination. It's the same logic with any expert, your plumber says your pipes need to be replaced

They are also the most competent and qualified to make that determination. It's the same logic with any expert, your plumber says your pipes need to be replaced because xyz, you don't believe them, they say it's your decision, pipe bursts floods your basement and takes your hot water tank with it. You call the plumber and have them do even more work and they take substantially more of your money. If they were actually out to make money then they'd wait until the infrastructure is literally dust at which point they can name their price and you'd have to eat it.