Re: Stepping on seats to get in or out
It can't be good for them, any nore than regularly standing on your sofa in the living room. If your boat is entirely upholstered, you have little choice but to live with it, especially if you carry a lot of non-boaters. If there is a removable cushion over a seat/hatch, take it off and encourage people to load there.
If you tell them not to step on the cushions, they will jump in, which is worse on the floor. You can try to encourage them to step over the gunwale but tide and design can thwart that effort. Just don't let them step on the seat backs or push on the windshields.
So if you want your boat to be enjoyed, then replacing the upholstery, or living with it wearing out, is a cost of doing business. INcreased luxury=increased maintenance and expense. Fiberglass seating with removeable cushions is the solution, other than being one of the miserable captains who won't let people relax on their boat.
For anyone considering buying a boat, consider this trade-off among your choice of designs.