unlike any other asset which requires a large investment, you can always buy small amounts of bitcoin.
for example you can not go to a stock broker and buy $10 worth of stocks! they wouldn't even let you and laugh in your face. or you can't go and buy $10 worth of gold, that is physically impossible.

• but you can buy $10 worth of bitcoin

whether one should invest in bitcoin or not is another question. it is a risky investment and some people don't like taking risks under any circumstances and the market fluctuations can ruin their sanity specially someone who is already in debt.