What you are saying is that a judge isn't going to rule knowing that he's wrong. One problem can be that the judge doesn't know he's wrong because the defendent didn't provide any evidence. Since judges are overruled by higher courts all the time, it would seem that they know there's that risk everytime they make a decision. In fair contests, where both sides have lawyers, the summary judgment is popular with the defense, to end meritless cases. Good for that. In unfair fights, where the plaintiff has a lawyer and the defendant is alone unaware of what to do, summary judgment seems popular with the plaintiffs. In those cases, I suspect it is possible, even sometimes likely, that the reason that the defendant couldn't resist the summary judgment isn't because the defendant really didn't have any defense.
Your right. I see it all the time wherein self-represented litigants lose simple because they fail in a procedural context. This is where having counsel pays for itself.