~snip~
This is one of the most important reasons. If you invest in Bitcoin, you can make a 100% profit from it, mostly when you invest in the long term. Investing in Bitcoin will also give you the advantage of learning a skill, skills like trading and investment. IMO, with Bitcoin investment, you can also control your finances.
People who invest in BTC are not necessarily those who will trade with it, especially if it is a long-term investment - and many simply invest and then wait for a favorable opportunity to sell. It also raises the question of whether people consider 100% profit to be a positive thing considering that huge sums of money are invested in altcoins with the obvious intention of making much more profit.
Invest only $10,000 in Bitcoin for 5 years, and you will make decent profits from it, but when you keep the $10,000 in your bank account for 5 years, you cannot use it to buy what you will use the money invested in Bitcoin to buy because the fiat value has depreciated. But the $10,000 invested in Bitcoin will yield profits, and you can use it to buy what you want to buy.
That amount invested over 5 years might result in a small fortune for someone if the price at the end of that period is x5 compared to today - but for someone living in the Western EU, US or UK, that is not an amount that means much. However, you should define what being rich means to you (or someone else) - because I started investing in BTC about 10 years ago when it was only worth a few hundred $ - and even with everything I've accumulated in that period, I can't consider myself rich considering where I live.
It is true that BTC offers an opportunity to anyone who is looking for an alternative to investing in gold, shares or something else entirely - but it is also true that such investment is still high-risk, not only because of the volatility of the price, but also because of the risks arising from the security aspect.
Few people know how to store their coins safely, and just one wrong step means you could lose everything. That's a risk you have to live with if you invest for the long term.