In practical terms, reproducing someone else's work most of the time boils down to redoing someone else's PhD thesis. Which is both not very interesting and doesn't help getting your own research done.
I agree that reproducing someone else's experiment won't help you get your PhD closer to completion (because you should be doing your own experiments and publishing no matter what, if you expect to land that lecturing position, i.e. publish or perish).
Reproducibility is one of the main principles of the scientific method (those papers shouldn't even been accepted if they don't contain enough information about how to reproduce the experiments they describe)
If an experiment is so complex that it can be compared to redoing someone else's thesis it can be either that the thesis is very simple or the experiment is so complex that it probably proves nothing.
Yes, I'm not arguing the foundations of the scientific method, just pointing out how it is in practice.
In every field you have the established base theory, the bleeding edge you work on, and a bunch of preliminary work in-between. Checking out references is important, but this is a recurrent process (as you need to check the references of those works too), and you only have so much time.
So what really seems to happen is only a few select works in any subfield achieve large citation index, and those stand a decent chance of being verified at some point, or at least they do have enough work trying to build up on their results that a systematic inconsistency would show up.