I'd argue that selling flaming ponies at every stable all around Tamriel is far more immersion-breaking than the crown store, but that's not my main concern. What's more important to me is that it would blur the distinction between in-game and real world money. You can put it in a separate tab, it doesn't matter, I still talk to an in-game merchant and see "give me your credit card please." I don't want it. I don't want to EVER be reminded about real money purchases when I'm playing.