I'm not certain what's changed over the years but I used to love going into Salvation Army or Goodwill and browsing their stuff because you never knew what cool thing you might find. Nowadays, they all seem to carry the same picked-over stuff.
I think part of it may be that they have also noticed the cool items and moved them to an online marketplace where they can get more cash for them.
With the rise of the Internet and ecommerce, there's now hoards of people buying all the good stuff to resell on Amazon, eBay, Craigslist, Facebook, etc. Many professional resellers go to charity shops daily.
I think part of it may be that they have also noticed the cool items and moved them to an online marketplace where they can get more cash for them.