Solipsism generally holds that only the self can be known to exist. But just because something is possible does not mean it is likely. If solipsism is false, it makes sense that the universe seems to have consistent laws and that past experiences are consistent with future experiences. Dreams, in contrast, barely make any sense and rarely remain consistent. So if humans were brains in a vat, I think the probability of our experiences being consistent with an outward reality would be very low.
I have the same doubts about the zombie theory. If your brain is generating consciousness, it seems unlikely that it would be the only brain to do so. It also seems unlikely that a non-conscious brain would lie and say that it was conscious, or be somehow programmed to act outwardly like a conscious mind. Even if this is a non-physicalist correlating effect, whatever external cause is putting minds into brains probably wouldn't stop with one individual.
You might be on the Truman Show, or the victim of some elaborate government conspiracy, but neither of those things is very likely. I'm not sure how solipsism is more significant than any other theory that is technically possible but very unlikely.