The problem is that allowing merges incentivizes zooming ahead in the merge lane, which should result in there still being drivers who can't merge, creating the jam. I don't have a good solution for this.
And if people were to implement this strategy, the provided space gives an incentive for those zooming ahead to merge a little sooner rather than risk waiting half a minute for someone to let them in right at the exit. It's been my experience that most of the "cheaters" will merge a little sooner if there's space rather than zoom up right to the end. They'll still be passing you, which is IMO aggravating, but at least things will move a little sooner.