I had the same problem with the auto renewal, and it seemingly being impossible to remove your credit card from their system.
I think with these next two systems, both of the companies are going to really, really, really, really want you to have a credit card connected at all times. It will be interesting to see, if you want to sign up for Gold, maybe it would "require" a credit card to be linked to the gamertag. The same thing could happen with a premium version of PSN. I think they will specifically "prefer" you having a credit card linked, rather than just having "points", that can be purchased with points cards.
Reason being, I could be a super cheap guy, and just put $20 worth of points in my wallet, but never put anything else in there. When my $20 is spent, the wallet has zero in it. Neither company, and ESPECIALLY the big publishers, are going to want that to happen. They want to make sure that they have a seamless access point to your money, when, and wherever possible. So, with their premium online services, they could easily "require" a linked, and active credit card, for the account to be valid.
At the same time, what about the accounts for kids ? There are tons of parents that aren't going to be interested in having their kids have access to something that is linked to their credit card.