Yeah, ‘we won’t take this seriously enough to actually cause real damage’.
It's to be a persistent thorn in their side and make the cameras more trouble than they're worth.
There are a lot more of us than them. If 1% of Americans cover up 1 camera every six months and it takes 24 hours to notice and uncover the camera, then there would be approximately 0 functioning cameras at any given time.
Think of it like the sit-ins or bus boycotts during the Civil Rights movement. That wasn't causing real damage, it was just a lot of people being very persistent about causing minor inconveniences. That wasn't the only tactic they used, but it was an important part of the movement's success.
Lawyer costs the same per hour either way.
Sounds like someone who's never had to hire a lawyer before. They vary in cost and quality, and there's not a 1:1 correlation between the two. There's also many different areas, eg real estate vs corporate vs labor vs immigration vs criminal.
As far as I can tell, the most likely charges for the garbage bag strategy where I'm located would be a maximum $500 fine, which is too low for most people to even bother with a lawyer.
If they wanted any jail time, they would have to try to frame it as obstruction of justice, which is a stretch and would be difficult to get to stick with a jury.