well I'm not saying it should be forced. encouraged strongly perhaps
an ATV is VERY different animal, since your already in a crouched position it is alot easier to hop off, since most mowers you are driving in a fully seated (in some cases almost stretched out) position, it changes the dynamic of the ride and the escapes. my brother in law will pop a wheelie and as he carries it up, step off the rear rack of his 450 honda. When I'm on a 4 wheeler, I tend to lift up off the seat when I'm doing things that will cause a roll, which you really can't do on a mower as you wouldn't be able to use the clutch or brake then
I don't see a mower as easy to extract yourself from as a four wheeler IMO. and thats why if you're like me and figure your going along for the ride, a seatbelt & ROPS doesn't seem out of line.
with your rear engine chris you could go exo
as I said, this is more lobbying for an option/allowance than demanding it as with brake upgrades.