I am fond of gift trades.
Gregies small engine repair is about a mile from my home. It's been there for about 40 years. The owner has candy for kids and treats for dogs.
When the owner repaired my mower two years ago, he told me it was pretty crummy. Even so he didn't want me to throw it out. I think for him engines are personal.
When I got tired of my lousy mower I went to him for a new one. I was too late though, winter is coming and he's done restocking mowers. He told me where to buy a new one.
Before I left, I gave him my old mower. It would cost me money to dispose of, and he wanted it. I didn't ask for money.
In return he gave me advice. He taught me how to adjust the strike plate in my old push mower, and now, for the first time I can remember, it seems to work. He told me to not to use my new mower on steep ground for more than about 20-30 seconds, because in a modern 4 cylinder engine the oil won't circulate well enough. 
He also, indirectly, explained why push mowers really can't really come back .
I appreciate these gift exchanges. They are one reason I rarely sell used items -- I prefer to give them away.
 In older 2 cylinder models the oil is mixed with gas, they don't have this weakness. There's more Free Advice on his web site. Good luck finding methanol-free gas in Minnesota.
 The blades must be periodically sharpened, and it is slow, tedious work. In a world where labor is costly they're too expensive to maintain. Push mowers can only really return if the sharpening problem is solved. (Significant money may await those who solve the sharpening problem.)