Oh, rider for sure.

I don't feel up to push mowing anymore.
I think you are missing what I said. there are plenty of GAS tractors that were running less HP engines than many rider lawnmowers are now.. if the small engine in a lawnmower doesn't have to meet an emission standard, why would it need to meet the standard in a tractor application? My current 12.5 hp rider mower is MORE hp than a few of my cultivating tractors.. think about it...
I disagree with your disagremment on gasser lie expectancy.
looking at tractors and cars.. which, given is not straight apples to apples .. Look at gas cars from 70's 100k and the car was ready to be a toaster.
I think much of it is design and materials. Throw away engine designs coupled with alumin alloys, and non peak rated hp output put lots of stress on engines made smaller... that wore out and were junked instead of rebuilt.. vs a heavier beefier design meant to have liners punched out, bearings rolled in and crank polished and rings replaced then ready to go another couple decades. IE.. their constant load design was reflected in their materials. So.. 30's-60's were robust... 70-80's got puny.. now here we are with gas engines that don't need tune ups till past 100k.
I'd deffinately call that a bell. high, low, high...