The more money you offer in remuneration, the more people will apply for the role whose primary interest isn't the job itself but the money.

Whose job entails more responsibility? The line-manager, or the person who fits the brakes or the seatbelts?

The janitor is vital to the company for purely practical purposes that have nothing to do with their humanity: it doesn't matter if you have a roster of 5-star Michelin chefs in the kitchen, if Health & Safety shut you down because your customers are catching typoid from your bathroom.