Some people knew about bitcoin during the early stage of bitcoin, they had the opportunity to invest in bitcoin at the early stage, but they didn’t invest in bitcoin. most of them didn’t have confidence in bitcoin, they didn’t believe bitcoin will get to the current price. Some people knew about bitcoin at the early stage, they even bought some bitcoin, but after little profit they decided to sell the bitcoin back, because they were thinking maybe after selling, bitcoin price will end up crashing, but bitcoin price keeps on growing.
Many of us like to criticize and laugh at people who knew about bitcoin early but didn't buy or sell early. But I think if we were in that situation, we would do the same thing because the future is unpredictable. Easier said than done, buying and holding bitcoin in the early days when the world didn't know about it or called it a scam wasn't easy.
Am sure people that think bitcoin price is already high right now, and they not investing, then am sure they will end up regretting at the end. If you are having money which you won’t be using for now, then I will recommend you do some research about bitcoin, and leave some money there, I will say bitcoin price is not so high yet, I can’t just image the price which we going to be seeing bitcoin price in the next 10-20 years.
It depends. People who don't invest in bitcoin now will likely regret it in 10 years if they remain poor and haven't found a better way to make money. On the contrary, those who do not invest in bitcoin right now but they have their own path, and become successful and rich. They will not regret skipping bitcoin. Like Warren Buffett or Gate, they refuse to invest in bitcoin but I don't think they will regret it.