There can be many explanations for very old untouched crypto wallets. The easiest explanation is probably that the investors don't really need the money and believe in the long term growth of Bitcoin. The bitcoin price had a good recovery in the last few weeks and some people could be interested in taking profits now. But if you have been around since the beginning of crypto currencies, you have seen the bitcoin price close to 70,000 USD. When you didn't sell at the ATH, why should you be selling today? Also with the halving coming up next year it makes a lot of sense to wait longer before selling. Another explanation why the coins in these wallets are untouched could be that the investor lost access to them, or the investor died in the worse case and nobody from the family knows about it. There are quite a few stories about people losing their keys and all their bitcoin.