What does it mean when a paper is rejected but encourages resubmission without a suggestion of new experiments?
Many journals are now encouraged to publish the data on the "efficiency" of the review process, e.g. the average time before initial submission and publication. Expected time to publication may be an important consideration for authors, along with the journals impact factor. 

So, imagine that you run a journal, where a paper on average goes through 2.5 rounds of review and each round takes 3-6 months. If you sum it together, 12+ months from submission to publication would not look too attractive. But you only need to sum up if you invite revisions. If you "reject and resubmit", then technically you look at a completely new submission, and it counts as a new paper in your statistics. So, your processing rate gets shorter (which authors like), and your acceptance rate gets lower (which makes your journal sort of a prestigious one, tough to get into). 

This is the main reason (in my personal opinion), why so many journals now rebrand "major revision" decision (and often "minor revision" as well) as "reject and resubmit".