Why does shipping quickly and often matter so much to so many companies? Is there any concrete study behind it?
These are some factors I can think of:
Rhythm: In one project that I joined towards the tail end, just before release, things were looking quite bad. The bulk of the work was done, but there were too many open threads left and the launch date kept getting pushed back, and back. One thing that we as a team decided that I think really helped was bind ourselves to a fixed bi-weekly release cycle. Product or management didn't ask us, we just decided it ourselves. Twice a week, at fixed times, the release train would leave. The overall effect was something akin to how someone who is hyperventilating can get back to a more relaxed state by breathing to a rhythm.
Statelessness: Every release is provides a mental closure. Sure, there are TODOs, and things that you realize over sleep that are semi-buggy or could be done better. But there is something out there. I'd die more peacefully if I were to get hit by a bus after making a release than in the midst of a cycle :)
Iteration speed: This is perhaps the reason specifically pertaining to programming. We're more productive with shorter feedback cycles. Let us think about an environment where doing a code change, making a build, and then seeing the effect of that change takes, let us say, 2 minutes. A different environment where this cycle is 2 seconds is a whole different ballgame. It is just much more productive. This same principle applies to shipping, just on a higher level.
Fear. Or lack of it. Bulky releases come with fear. Software is hard, there are just too many things that can interact to cause unanticipated effects. The shorter the release cycle, the less the fear of the unexpected stuff happening. And when unexpected stuff does happen, it is easier to zero in on the cause.
Of course, there are downsides too. "Release fatigue" could be one. Diluting the importance of the release could be another - a sentence would look pretty tedious if every. space. was. replaced. by. a. fullstop. I personally try to do it as often and rhythmically as I can get away with.