E.g. there’s increasingly an expectation that students should come into a PhD program with one or more publications already under their belt. For top programs ideally these should be first author (not yet an absolute requirement but it’s more important each year).
So you better get a good research assistant job as an undergrad so you can do that. It has to be early enough in undergrad that you have time to get the paper out before applying to grad school. So you need to be prepared to get a professor to work with you freshman/sophomore year…
So you have to have evidence of skills basically coming in to undergrad. Either be really brilliant and stand out in class, or, better, have some experience in high school to make you credible…
These pressures would only increase with fewer PhD slots. Maybe that’s fine long term but it does have a distorting effect on people’s lives if you have to make high stakes decisions that early.