Busywork, which I consider logo change to be, doesn't really make a project seem "maintained". But at least it's not a productivity-disrupting change so... whatever floats their boat.
It's not the regular change of logos that people notice and then think that that must mean that the project is active.
It's more that design trends change with times, and color gradients currently went out of fashion (but will come back, in a later design trend), so it's important to adapt to current design trends once in a while.
If you don't do that, people subconsciously dismiss the software without trying, assuming that it won't run, or won't be able to handle modern workflows.
No users -> no contributors -> project dies.
You've seen benign instances, then. Every time I see a company do this kind of thing it takes one or more engineers nontrivial time to go update everything.