Many people act differently when there's awareness of being in the view field of a camera.
It's the whole premise of the classic "Panopticon" prison design, much has been written about it.
This can be in play regardless of whether one believes the camera is or isn't recording.
Especially if there's uncertainty about whether the camera is recording.
Its a psychological reality for many normal people.
I trust in GOS' toggles and my device's security...
AND I cover the cameras.
So that I don't have to look at the cameras and wonder "did I slip up...?"
We're all physical animals who make mistakes sometimes.
The physicality of the covers can matter to some.
They are easier to verify -
a single self-evident glance with physical covers
vs
turning on the screen (and perhaps even needing unlock depending on the settings) to check the toggles
Also, "security in depth" encourages a layered approach.
Even if a device is compromised, at least this one aspect of its data collection harms could be mitigated with physical covers.
Its cold comfort and the least of one's problems in that scenario, but still non-zero harm reduction.
Just my personal take.