Some people have services only payable through Bitcoin. Mind you, they are legitimate services. I've never bothered with the dark web nor will I ever. I just find it a convenient and in-a-way "safe" thing to use than services like PayPal.
Right. paypal got large transaction fees unlike bitcoin where you just pay a little satoshis to pay online services. Those satoshis converted are just like cents to dollar. Bitcoin would be the right choice.
Good perspective. One query paypal has high transaction fees, but when you use bitcoin there is not much services accepting bitcoin. Also if you do exchange and use your bitcoin the exchange rate is low. Finally you would be paying value equal to what paid through paypal.