Lost coins only make everyone else's coins worth slightly more. Think of it as a donation to everyone.
Well... this is very much true. Bitcoin offers a lot of advantages to its users, but also comes with a few riders. If you don't know how to backup your coins, then you should not hold BTC. The problem is that many of these early investors purchased their coins when they were really cheap, and then forgot about them. Now with the prices having increased to five digits, they want to cash out. I still remember the story about a guy in the United Kingdom, who threw out the hard drive containing
BTC15,000 in a rubbish dump, and then spent months looking for it.