I have often thought about this myself.
I never want to advertise the fact that I have guns. As was mentioned, there are a number of reasons why. I guess the two biggest reasons would be theft, and having uninformed/brainwashed people thinking you are a nut because you own guns. Whatever the reason, I can't think of ANY good reason to let other people know you own guns. Even though I am not doing anything wrong, I always try to put guns in my vehicle so that no one sees them. I have thought for years about buying some kind of cases that appear to be something other than gun cases. The problem is that gun cases are cheap. I have never shopped for something like a guitar case, but I always assumed that they would be significantly more expensive. And, I frequently take more than one rifle to the range, so I would need several.
I don't even like to get packages sent to my house that are obviously gun related. Again, I am not doing anything illegal or immoral, however in today's society there are many people that think that gun ownership is wrong no matter how responsible and safe I am.
You know the rest. In the books you have read
How the British Regulars fired and fled,
How the farmers gave them ball for ball,
From behind each fence and farmyard wall,
Chasing the redcoats down the lane,
Then crossing the fields to emerge again
Under the trees at the turn of the road,
And only pausing to fire and load.