I know this is a zombie thread but it <pokes> seems to have revived a little. I rarely leave washing out overnight and my washing line can only be seen by my immediate neighbour, and only part of it. If I have to hang my knickers on that bit of the line I always make sure the gussets are facing away from him 
I came across this Unherd article a while ago but didn't read it because...yuck! However, this thread prompted me to go back and find it
https://unherd.com/2025/05/depops-dirty-little-secret/
I've always known men fetishised women's underwear. For so long that I don't even remember when I learned it. Blokes buying used pants of Vinted or from an only fans is one thing. You'd think with the rise of the Internet which means they could buy their own without the potential embarrassment of going into a shop they'd be...a lessening in demand, in thefts.
Anyway, my reckon is that there hasn't. I think in some cases it's a gateway. It'll escalate as legimately acquired drawers just don't do it for them anymore.
There is a Canadian serial killer, Russell Williams, who began by stealing pants, then burglary, then rape, then murder. He was in their armed forces. There are photos, bizarre selfies, of him grim faced in women's sexy lingerie he'd stolen. The last I heard he was in a male prison. Perhaps even Canada thought putting him in a women's was too far. Or perhaps he hasn't asked yet.
If the Police aren't treating underwear theft like voyeurism and flashing as a sexually motivated crime then they're idiots.