People are hopefully not locking up bicycles with power meters, or full Dura-Ace di2 or similar in public to be stolen by the local metro area's drug addicts.

Anybody who lives in a sufficiently large city, and rides a bike worth more than about $1,000 or so, knows that they will never be locking it up and walking away from it anywhere.

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.