What if a person uses it to buy something that will help them get more Bitcoin (i.e. investing in a business)? Doesn't seem economically irrational to me, so l

What if a person uses it to buy something that will help them get more Bitcoin (i.e. investing in a business)? Doesn't seem economically irrational to me, so long as the return is greater than the increase in value that would be gained from just sitting on it.