Not sure that they do. They could, but I don't know of any significant video editing plugin ecosystems on iOS. Stuff's too rich for my blood—$200 to make overlay text look a certain way? $400 for a noise-reduction algo? Not for me and my casual stuff. Again, if you want actual pro software, you're looking at one of a couple desktop application vendors, that's true. If you're looking for pro-tier software for home use, and learning that pro-tier software is your main goal and/or you actually need what it can provide, then you're probably talking Adobe Premiere, specifically, and yeah, that's desktop only (and about $250/yr). If you just want to learn the process and techniques of non-linear video editing and put together (potentially quite good) edited videos or films, the iPad's capable enough (with the benefit that, in the original use case posted here, it's also a damn good drawing tablet and you can use it to shoot your videos, too, again, if you don't have actual pro-level needs), but I wouldn't argue it replaces a desktop with Premiere, for a bunch of reasons including that everyone assumes you've got Premiere (and often Aftereffects, too) available, when it comes to plugins.
