Why is the swingarm design uncommon / rare on full suspension bicycles? While watching a snow biking video, I saw that some of the bikes use a true swingarm design, which matches most motorcycles (as does much of bicycle technology). While this looks rather interesting, I'm wondering why it's so uncommon (and much more common are multi-linkage, seemingly more complex designs)?

I've found the bicycle he was riding, a Chumba F5, shown here:



Upon more searching, it's also used on Mountain Cycle Fury Frames and Motoped Kits as well, but an overwhelming majority do not use this design.

If I had to guess, I'd say it was solely weight concerns to not use this design with less moving parts. It also (seems to) allow for more travel, so is there perhaps an upper limit on how much travel you can get with the multi-linkage design?

Further, I've seen the Y-Frames (especially on BSOs) criticized for having poor flex characteristics. Does it again just come back to the weight issue in that more reinforcement is required for these designs?
This swing arm design has fallen into near complete disuse in the bicycle world for 2 reasons:


First, there is translated suspension activation from pedaling. This design does not isolate pedaling or other rider generated forces from ground generated forces. Because of that, there is a loss of efficiency which makes it a poor choice for a bicycle suspension design.
Second, the travel path of a single pivot swing arm carries the wheel forward as it moves through its travel path, because of the arc described by the wheel. If your rear brake is in use, the wheel is prevented from following that arc, and some or all of your suspension travel is lost until the brake is released. In a 4 bar linkage design, or similar vertical travel design, brake activation does not prevent suspension activation. Thus it has become the default design for high quality dual suspension bikes.