For the same reason that increasing headcount never really solved the bug problem.

Flawless software isn't the goal, ever. Feature development is almost always the primary goal, and fixing bugs and performance issues is only done if the bug is bad enough.

I don't think you're wrong overall, and it jives with tripleee's reply, but I don't think wanting end-user software to be less buggy than it currently is is asking for "flawless" software.