Bitcoin allows money to be sent anonymously across a peer-to-peer global network, with no intermediaries needed to validate or process transactions. That has made it attractive to those who want to keep their identity secret, including those buying and selling illegal goods and services on the internet.
Being able to keep the users anonymous is the main thing, apart from that there are other advantages too but that doesnt mean that there are no disadvantages too. Other advantages of Bitcoin includes being able to prevent fraud; unlike credit cards there is nothing like a charge back.
Another advantage is that with bitcoin youre able to avoid identity theft; no one can steal your identity just like they will easily do when you are using a credit /debit card.
And as others said, bitcoin is fast for making transactions and that leads to immediate settlements. There are other advantages as well, but these are the main ones.