Do programmers in Google not use Google to search questions? Do they not have self respect seeing the bad quality product they’re throwing up on billions of people every day? I can’t imagine working like that.

In the society I live in, self-respect doesn't pay the bills. I don't know where you're from.

Absent that, it sounds like the sort of excuse greedy people have always used to justify profitable harm.

Not really. Google has an excellent intranet search engine and mostly relies on in-house tools instead of commercial services (see https://github.com/jhuangtw/xg2xg). As a result its employees don't really need to rely on Stack Overflow, etc.

Google has caused this problem by rewarding blogspam with high search rankings. Maybe they're trying to fix that, I don't know -- but if they are, they've already failed for at least a decade now.

I'd lay long odds Google stopped trying to rank pages themselves for those common searches long ago. Instead they look at what results users clicked on for a given search, and they are listed near the top. With a bit of randomness thrown in, so it can learn when new results become preferred. While saying it's a AI learning what to return for a search might be over the top, it's I doubt it's too far from the truth either. But you need a lot of people searching get the data to train the AI. Maybe Bing suffers from not having the users.

I'd also lay long odds that the search results are weighted by the ad revenue they generate for Google. Ie a site gets a boost if it is more likely to generate ad revenue for them if the user goes there. Competitors limit how far that can push that - they still have to be the best search engine. But as their primary goal is to earn money via ads they just need to be slightly better and use the remaining headroom to maximise ad revenue.

This is pure speculation on my part of course, and mostly evidence free. But I'm pretty sure Google engineers are smart enough to identify quite a bit of the SEO spam I see in the top of their search results - yet it remains there. This would be a quandary - if it wasn't in Google's interest for it to remain there because the spammy pages inevitably contain huge numbers of ads, and Google is at the end of the day an ad company that makes money from people clicking on ads.