They aren't denied points. They can make the decision to just continue on and not get that point, or drop back and re-attempt to legally pass.
I don't recall specifically what the reasons were for making it the way it is, but the alternatives would be to either:
- earn the point if the jammer passes while both are out of bounds
- jammer only gets one attempt to score on any opposing blocker
The first provides a disincentive for blockers to go for big blocks anywhere near the line, leading to (likely) less exciting gameplay.
The latter is something that used to be the case, and was called "one shot scoring". It was overwhelmingly voted out. That was before my time, but I suspect the reasoning was that it made things much harder for jammers, and was arguably more difficult to keep track of as a jammer referee.
In any case, the way things are now is less punitive and allows jammers to make a choice based on what they think will give them better results. Maybe it's dropping back to get that one blocker point. Maybe it's moving forward to start a new scoring pass and potentially another 4 points.