First of all, there are two main kinds of BJJ. There is sport BJJ and there is self defense BJJ. There are many BJJ moves that would be great for tournaments but would be horrible for self defense (e.g. collar and sleeve/arm grips, they leave your face vulnerable). There are also some moves that are great for self defense that might get you disqualified in competition (e.g. scissor take down). Just because you have not learned any slams does not mean that they aren't part of BJJ. They just aren't part of SPORT BJJ.
I have actually learned a few slams during my time doing BJJ. For example, if someone puts you in a headlock, you can pry their face to the sky and reach under their leg to pick them up. Since this has no use in competition, it was made for the purpose of self defense. We practiced "slow-dropping" them, which is to help teach us to just drop your attacker onto the ground.
And remember, there is a large difference between sport and self defense BJJ. Just because a move isn't legal in competition doesn't mean that it isn't part of BJJ (for example, the scissor take down). You can also turn many techniques into slams. For example, a basic hip throw can be done with extreme force to "slam" your attacker's back onto the ground.
When people say that Jiu Jitsu is great for self defense, I would argue that they are right. No one ever claimed it to be a comprehensive all-inclusive self defense system, but it is probably THE most helpful grappling art for self defense (just my opinion, of course). For more backup, look at one of my previous questions: Why isn't striking part of Brazilian Jiu Jitsu?
But not only don't they train that, they actively encourage falling into a slam, due to the notion of "pulling guard".
Guard is a great position, although it does come with some risks: Groin attack danger in full guard (especially stages 3, 4)?
If you have your attacker in your guard and they start to pick you up, LET GO WITH YOUR LEGS. Nothing good will happen to you if you stay attached to them. There are several sweeps that you can do once you let go, including the overhead sweep and the Omoplata sweep.