You can buy drugs and other illegal things off the internet (tor), that's very useful for some people. Basically crypto allows for transactions that could otherwise be blocked or easily tracked by central parties (1). It can also be used to bypass gambling laws.

For legal purchases and activities crypto is useless, regular money is much more practical.

[1] depending on which crypto and how it's used tracking is possible, so care is required (especially) when converting dollars to crypto.