If by "logical" you mean "practical" then the reason is that the study which cost a lot of money to do, the constituent studies that generate data, are more likely to get a press release, and that is how non-specialists learn about new studies. Logically, from the perspective of the university, being able to point out the result of spending a lot of money to contribute to human knowledge is important, so they publicize these expensive studies. The metaanalysis is cheap, and takes a few people's time for doing the analysis, no new expensive data involved.