The idea for the side arm as it was explained to me is 2 fold.

1.) when you're in the middle of being attacked (meaning your already on the ground or within touching distance) the side arm is far more maneuverable and the long gun has probably been dropped. I'm not a big fan of this idea but its not entirely without merit. I'm sure you can find some vid of a guys gun jamming while a boar is charging and him getting it with a pistol but I think this is the exception not the rule.

2.) And this one I do support. Is on long multi day hunts you have a high likelihood of running into stuff around your camp. It's a lot easier and faster to have a pistol on your hip while carrying fire wood or going to the bathroom, or cooking than a long gun on your back. Its also more of something to make a lot of noise and scare it off.

I never carried one in Texas but for elk I carried a 45. Not sure if id do it again though. maybe a Glock but that 45 got HEAVY by day 5 lol