What list are you talking about, exactly?

There could be two (not mutually exclusive) reasons for the shorter iOS updates:

1) It's newer. Thus more exciting. It's something most developers yearn for.
For example: I have been writing code for the same industry standard software for over 8 years now. And it's time for me to move on, to start a new project, to do something different.

2) The iOS products are much younger than the Desktop version. Which means they have fewer features in comparison. The Desktop version has pretty much everything I need* and I'm not aware that people are missing that many features**. DVDP for Desktop has basically entered the maintenance phase of the software product life cycle.

* The feature I'm missing - and many others for that matter - is an overhaul of the cast/crew system. But somehow I get the feeling Ken has become scared of the challenge it poses. It's been over a year (almost two?) that he asked for ideas on how to change the system and never ever really came from it.

** One repeatedly asked feature is the ability to add digital media. But since these files don't really have any kind of Id to make them identifiable and thus profileable I doubt it's ever going to be a feature.