If you read your credit card's agreement statements, that actually makes your card invalid. If you look below or around where you normally sign the back of your card it says "Not valid unless signed." You'd be hard pressed to win any legal matter where you proclaim the signature of your name is "See ID."
In addition, so may retailers here in the USA have swipe-yourself terminals. The clerks rarely, if ever, actually look at the cards now. It still happens, don't get me wrong, but how often does a minimum wage employee actually ask for your card? I didn't have it happen too often when I put my signature plus "See ID" on the back of my cards, so I just stopped.
Hell, my job they told me to stop checking as it wasn't in our policy and none of the other cashiers bothered and it was just confusing the customers. And you will get more flack from the customers for checking signatures and for IDs if it says check ID or isn't signed than you will for not checking. As much as I wanted to check cause I have that myself on the card so I feel like a hypocrite not checking, I'll have to say it has made my job a lot more pleasant cause it reduced 75% of the reasons customers yelled at me. It's amazing how many people get pissed off if you ask them to take 2 seconds to bring out an ID to help prevent thieves from using their cards (people just don't care. I think they just figure the credit card companies will sort it out. I personally would rather not have to hassle with contesting charges in the first place. That to me is a helluva lot more hassle than bringing out an ID).