How was it before then? Surely you can't expect that N PhDs minted by one doctoral advisor will each be able to take an equivalent spot at the same institution as the doctoral advisor. Or did people expect that? Unless the population is growing, the steady state is that one prof can only mint one prof-descendant in their lifetime on average. That means, maybe some can create more, but then some will not have any mentees that ever become professors. It is very basic math, but the emotions and egos seem to make this discussion "complex".