I'm not sure what's behind the decline. Apple had a public beta for both, but public beta programs now have more to do with marketing and promotion than they do about finding and fixing bugs. Also, iOS and OS X are both on a tight release schedule where there's not much wriggle room for delays.
But buggy software is still buggy software, and it sucks for consumers who have paid top dollar for products to be encumbered with so many issues. It makes Apple appear slapdash and lackadaisical, especially since it has such a tight control over the hardware.