I've noticed that when I use Privacy.com on a some SaaS sites, the site already declines the signup saying something like "we don't accept temporary cards".
I can't remember which right now, but I know I've seen the error message a few times.
Privacy.com issues you a card that is coded as a prepaid debit card. Most payment providers expose this to merchants, which means that if they choose to decline prepaid debit cards for other reasons you'll get caught in the mix.
Sometimes credit cards are used kind of like collateral... when you stay at a hotel, for example... you give the hotel a credit card for 'incidentals', and it is basically being used as a guarantee that you will pay for things you are going to use. Car rentals are the same.
In a sense, it is your credit card limit is basically your credit card company saying "yeah, this person is good for x amount of money". That isn't much for a prepaid card.
Yes I've noticed it too. I think they tell them this because Maybe it's to prevent freeloaders from creating multiple audible, Netflix, etc trial accounts?
Unfortunately it also defeats the legit purposes too.
I can't remember which right now, but I know I've seen the error message a few times.