Dude, this is nonsense. Everyone regrets passing up on buying BTC because it's currently worth $6k because you can sell it right now for that money. Anything else is complex rationalization to make yourself feel better.
I made what I believed was a rational risk assessment at the time (back when MtGox was spinning up... Not exactly the most credible days for BTC) and decided to avoid the hype.
Could I use the money now? Sure. It's money.
But I don't regret the decision now because I was acting on the information I had.
Heck, even now, it's possible for someone to buy BTC and for it to crash. Should those people regret their decision even if, in their estimation, it's rational now?
To be blunt: if you spend any time regretting these types of things you're a gambler, not an investor, and will find yourself tricked into trying to time markets. And that will eventually bite you in the ass.
As for me, the same reasoning that kept me out of the market then keeps me out now: I don't believe in the fundamentals and I'm not a gambler. Full stop.
For those who do, the should buy and hold for the long term to realize the most gains.
But "it's worth a lot more now than it was 10 years ago" is not fundamentals. It's just the irrational assumption that past performance predicts future behaviour.
My life isn't a lottery ticket.