This is a good point. A decade or two ago most of the manufacturers built their engines really tight. Both Toyota and Honda manufactured engines, that with good care could easily go 300,000 miles or more...... And didn't burn or dilute the oil in the crankcase doing it.
This is no longer the case. Low tension piston rings, along with direct fuel injection have polluted engine oil in as little as a thousand miles. Not to mention they've all gone turbo crazy, which puts even more demands on the oil in them.
There are literally dozens of Internet videos showing both severe fuel dilution of the oil, as well as gunked up piston rings, Many of them have been posted here.
On Toyota and Honda engines that used to be built tight as a drum, before all of these government mileage regulations started piling up, are now forcing the automakers to go to these new manufacturing standards of "free rotating" crankshafts, coupled with low tension rings, and direct injection.
The new game in town is to get as much power and mileage from as small of a displacement engine as possible. That is difficult, if not outright impossible to accomplish without pushing the oil in these modern engines to the max.
And there is little to no doubt the government, along with the EPA is pushing all of this to the max. They HATE anything that runs on fossil based fuels. And they couldn't care less how much the average consumer dislikes it.