2015 is not too late, most cryptocurrencies did not exist and people were just buying and selling bitcoin.
trading bitcoin and altcoins was not like we see today. coins was mostly bitcoin and some other alt

Before that there was one MtGox and it was and everyone would buy from it.
At the present time it is easy to buy bitcoin and buy a lot of it or trade it with altcoins without needing to verify identity or many technical complications.