Every time there is an ATH, this story always resurfaces from Wales:

https://www.walesonline.co.uk/news/wales-news/man-who-threw-away-bitcoin-28833001

In olden times people just didn't take much care over their Bitcoin, especially in the first epoch, as they weren't worth a great deal, and you couldn't do much with them. Remember that 50 Bitcoin were being produced every 10 minutes.

I personally have had paper wallets that I keep in amongst other paperwork, just the sort of monetary value you keep in your pocket at the time. I had BitcoinQt on an old laptop that broke in 2014, and that just got thrown out.

So I can believe that many are lost.