The job market right now in the US forces grad students to attempt innovative research with remarkable conclusions. As a consequence, everyone's trying to prove more outlandish things while few are bothering with replications. If the field were sane, you would train all the apprentices on replication studies. Once they demonstrated dispassionate expertise with the tools, only then would they be allowed to try to use…
Apprentices work on papers and research for their professors. No one is incentivized to do replication work: either you replicate it successfully (great) or you find flaws. In the latter case, you'll probably be a nit-picker anyway—also not really additive. On the off-chance that you refute a high-profile study (e.g., some of the outright instances of fraud), you might get some recognition, but now your name is associated with something negative (e.g., fraud: "X is not true") vs. positive ("X is true").
Finally, this is some of the role of review panels in journals: too pass the burden of proof.