It's your husband's account, and his field so I'll let him make his own decisions.
I didn't think too much of it, because how else would Ebates deposit the earned MR points into my Amex account? They can't exactly mail one of their Big Fat Checks.
I've used Ebates for years, and similarly I've given it access to our PayPal account because that's where my cashback payments get deposited automatically every quarter. I just found that much easier to deal with, faster, and safer than having a check mailed to me.
Again, I'm not trying to start an argument. Just my experience.