Maybe not those accessories in particular, but what of the rest of the bike? Tons of bikes are clearly getting stolen.

I think a lot of them are just cheap crappy bikes that get cut up for scrap too. Someone stole my heavy-ass steel 90s Schwinn mountain bike that was worth maybe $50 used at the time. I had a big ass lock on it too, and they cut right through it with one clean snip. I was pretty pissed because I had just fixed it all up, but there weren't any expensive components on it... Not sure what kind of money could be made on it. Maybe a few bucks at a pawn shop?

Also around Seattle, I have noticed a lot of places that look like homeless camps, but right smack in the middle is a huge pile of hundreds of bicycles. Just sitting there outside. Part of me thinks that a lot of bike thefts could be mentally ill people collecting and hoarding them.

I agree they are, but from watching the several local social media groups in my metro area which are trying to keep track of stolen bikes, everything that I see stolen, if it were road would be Tiagra level or lower components, or if MTB/city bike would be deore equivalent or cheaper.

The main exception would be downhill bikes that are occasionally stolen from garages.