Credit card activation: security or reverse marketing?

So I received two new Discover cards , with supposed enhanced security features. I didn't ask for them, they just sent them to me. I got a new account number which is a pain because various merchants directly bill my credit card and they will have to be updated, by me.

You know the little stickers on the credit cards, call xxx-xxx-xxxx to activate your credit card? Do they actually do anything or add to security? Would the card not work if I didn't call the number?

Well the nice lady who got on the line to activate my card promptly switched scripts and (after thanking me for being a customer for sooo long) promptly started selling me something.

How annoying. Tricked me into calling them to get their sales pitch.