To attract the customers, airlines are posting low ticket prices that don't, or only barely cover their costs.
Therefore, they must claw back as much money as they can by charging for everything they possibly can. So tea, coffee, sandwiches - (even alcoholic drinks used to be free - included in the ticket price) - are intensively sold on board, your suitcase in the hold, sitting together with the others in your party, a seat with (any) legroom, an airport that is in the city it pretends to be in, instead of actually being 30 miles away, paying to choose a seat, using very cheap baggage handlers, setting off at 0500 or 2300, printing out your own boarding pass using your own printer, paper and your own ink, having your knees almost touching the seat-back in front of you, paying exorbitant prices for car parking - or even dropping passengers off, using agency engineers instead of employing their own.......etc etc.
Many years ago, when the LoCos were getting started, I thought to myself that the CAA should legally mandate ticket prices being above a certain minimum, and that money ring-fenced to ensure a certain minimum level of safety, service, maintenance and standards. Beyond that, airlines would have to compete in other ways to attract passengers, e.g. by providing a better service, employing their own service staff, or providing extra frills, etc.*
*+ carrying spare seat cushions !