Along the lines of what Max said, OEM's "design to cost". Good example back in the '70's or 80's forget which (brainfart), One could compare Ford Pintos to Cadillac Sedan DeVilles. One cost $3k, the other $20k. Both were designed to cost; i.e. they were designed with the selling price in mind. Obviously you can't put a gold plated widget in the Pinto, but that is not the market the Pinto was designed to satisfy.
I like, use and have used Kohler whenever I can. Currently have 3 Command engines, all singles up thru 20 hp. I also have a BS engine (22 HP V) that is built for the commercial market. It is a far cry from the engine that you get on your 20" push more at the local save-a-dollar store.
I'm not pushing any brand but currently have 2 0Ts and 3 regulars. The 0Ts were hard for me to get used to initially, but now I use the little 44" Hustler with an 18 V Honda the most. It's just handy; I have the front deck to carry things, and frontal visibility is excellent. I put bar lug tires on it as I mow pool (pond) banks and other things where I need traction. I use the larger one for mowing larger areas and trimming the fence line around the pastures; put bar lug tires on it also. It is a 52" and having the wider deck gives me room outside the tires to get under fences.
I use Full syn oil only, and change oil once per year, or if it gets dirty which usually doesn't happen....with syn. Have had zero problems with any of these machines, except a little Scotts with the 15.5 K and wore the deck out on it. Had others so just parked it; course it was pushing over 10 yrs of usage. Engine/tranny are still in excellent shape.
HTH,
Mark