You must all be off working on those animations, cuz ya sure aren't in here. These threads are getting dusty.
I would imagine these might be some reasons why people don't bother with animations:
1. Many (most?) individuals familiar with various forms of locking mechanisms can grasp a new concept fairly quickly and easily visualize it for themselves from text descriptions only.
2. Most schemes in the early phases are very rough and will probably have flaws which will be revealed as the posts mount. Creating models and animations is a lot of work for something that you'll just have to revise, perhaps radically, who knows how many times before you have a solid design. That's a lot of extra work and wasted time.
3. You may invest considerable time and energy into creating an animation only for someone to point out later that it isn't an original idea afterall -- e.g., a patent already exists on that design or very similar. This information could most likely be provided from text alone (see 1 above).
4. If it's truly an original scheme, either before or by the time it has been subjected to sufficient public scrutiny so as to find all -- or at least the majority -- of its flaws and corrections suggested/made, the original inventor is probably no longer interested in the design being open source and would instead investigate the potential for a patent on the
refined design -- with all due gratitude to the helpful contributors in the process, I'm sure.

Ergo, said refined design wouldn't be revealed to the world and may be radically different from early animations, rendering them null and void -- again, a lot of work for nothing, especially if that patent fails to go through.
Of course, the amount of work involved is directly proportional to the design's complexity and, therefore, the need for providing adequate views of all the components (perhaps in motion and complete cycle of operation as well for utmost clarity).
If it's a super simple design, then a simple 3d model will do. But, if it's a super simple design, it's probably been done already, rendering [pardon pun] the model unnecessary.
If it's a highly complex design, it may necessitate modeling numerous components (unless a bunch are the same and it's a copy-paste job) plus the animations demonstrating their interaction, and multiple transparencies for clarity [pardon another pun]. That's potentially a huge amount of time and effort for little to no gain -- unless, that is, the whole idea was to have others work out the problem areas for the inventor as he finally runs off to the patent office with the refined design.
I realize this is just a hobby with a lot of people, but there's still a difference between
spending time on a project and
wasting it.