I live in Texas. There were two issues I ran into that prompted me to support open carry.
The main issue I had, pre-open carry, was that if I was carrying concealed, and I reached up to get something off a shelf at the store and my shirt/jacket/whatever raised up enough that any part of the firearm was visible, then I was breaking the law, even if for only a second. I personally had police officers write me a ticket for that. Now with open carry, that's not a problem.
The other was when I'm out at the farm and open carrying there (snakes and wild dogs [f-ing assholes come out and dump their problem dogs in our area: they are not afraid of people, but get mean and vicious real quick, and like to eat our ducks and chickens]), and then I need to run into town for something, if I forget and leave my pistol on my belt, it's no big deal now, and all nice and legal.
Usually before I would realize it as I got out of the truck. Then you're stuck either finding a shirt or jacket to cover up with, or taking off your pistol which then leads to where do you store it? And what if it gets stolen while you're in the store? And what if someone sees you while you are taking it off and gets the wrong idea. So yeah, open carry is nice.
I believe that it was during Reconstruction that Texas banned carrying swords and Bowie knives, and concealed and open carry of handguns. We finally allowed licensed concealed carry in 1994. In between if you wanted to carry you became a reserve deputy or reserve police officer. Then you were a cop, so it was ok. We had lots and lots of reserve cops. Not so much, now.