This comment section is all people missing the point.
The point of the post is that a particular job will generally stabilize at a particular pay. If it's a tipped position, then the employer will pay less, so that the overall income is roughly at that stable income for that position, including the overall average tip.
So people who tip less than the average are free riding off of the people who tip more than average, where that worker will make an average tip overall, which comes more from the generous tippers than the stingy tippers. Thus, it effectively transfers money from generous tippers to stingy tippers, on net, in the long run.
The merits of this system, whether servers deserve to be paid more, whether we should push for reforms so that this isn't the system, is besides the point. The post is making an observation of how things actually are, not advocating for how things should be.