I wouldn't call it stupid. It's more about risk management. Consider this: In 5 years, what are the odds that Bitcoin will be worth more than it is today? Then consider your alternative investment and ask the same question.

Smaller cap coins can appreciate more than BTC and ETH, but they can also go down 99.9%. Unfortunately, I have a few of those in my portfolio. BTC and ETH provide a foundation for my portfolio.

Of course, everyone's goals, needs, and wants are different so invest in what makes the most sense for you.