It has nothing to do with fear. Have you ever tried to call in and cancel one of these services? If you're even able to find the right number to reach anyone, or after you've already waited an absurdly long time to do so, you'll be transferred around until you get frustrated and give up, or be subjected to extremely aggressive sales tactics trying to pressure you to stay on. I got to the point with one of those DNA sites where I had to ask about next steps for legal action to the representative before they'd even consider getting to the step where I could cancel my subscription - and even after that, still got charged and had to call again.
It's maybe comforting to think "oh, people just don't want to call, they'd rather eat the fees" when this is way over simplifying the problem and giving way too much credit to sites that operate this way.
(in the UK) it really depends on your bank and even the type of card you use. the debit card chargebacks I did when I was with Natwest were always very simple. fill out a form, send it off, get a response by email. for the one CC chargeback I did I think it required a call and a lot more trouble. when I tried a (debit card) chargeback with a different bank, it was an incredible amount of trouble and then I think they rejected it anyway
It's maybe comforting to think "oh, people just don't want to call, they'd rather eat the fees" when this is way over simplifying the problem and giving way too much credit to sites that operate this way.