It never occurred to me before.
I used to not, but SDMB bedbug expert mozhron has made me paranoid, so now I do.
If the clothes smell like Thrift Store, I wash them first. Well, I typically give them a little while to air out and then decide. Usually, they just smell like fabric softener or dryer sheets, which means they smell better than my freshly-laundered-with-eco-friendly-detergent clothes do.
I highly doubt that clothes are laundered by the thrift store before being put on the racks. But I think many people donate clean clothes.
Just bought some new jeans, which came with a “wash before wearing” tag (though I would have anyway).
For what it’s worth re: thrift stores cleaning clothes before putting it out. I recall a girl who said she worked for Goodwill years ago, and she said that they ran everything through the laundry before putting it out. So at least some thrift stores do launder everything.
So, if you think that perusing the underwear rack there is icky, imagine being the one who had to put them through the washer before they hit the floor.
Back the the OP-- no, usually not I love getting new clothes and I can’t wait that long to put them on! So far, no ill has come of it.