~ Why do people hodl rather than sell and buy again when low
Any BTC price is low. 15k was low, 69k was low; 1m which we haven't seen yet, is low too. And so is 100m.
Those who bought BTC when it was $1 and have held it until now, have probably done much better than anyone trying to time the market.
There are, however, not many such people. Those who bought at $1 sold it at $10, those who bought at $10 sold at $100. Then maybe bought again out of FOMO when it hit $500 and lost by selling on a dip to $50. A nerve-racking game. Meanwhile, those who have held have made a 20000x. It's much easier and less stressful to stop watching the charts and keep holding until you stop DCAing in (a.k.a. retirement), because the ultimate value of BTC is infinity.
Do you realize that in order to reach $1 million market cap should be around 21 000 000 000 000? I can't say that's not possible, but that's a pretty big goal and I'm not sure if we'll ever see that. When people say that BTC's value is infinite it sounds kinda crazy, like you're from a cult.