This is how I travel occasionally as well. The built in allows you to be fully self contained with ease.
Pin Box mount is not a bad idea, but not quite push button convenience. You have to protect the genset from the elements somehow? You have to get out the cord, put it away, start the genset outside....maybe you have remote start? Hopefully you have electric start and not pulling a cord!
Lastly you have to refuel the genset which requires carrying gas cans, maybe a ladder or stool to reach genset. If you vehicle is a diesel gas is a fuel you otherwise would not deal with.
If your vehicle is a gasser, gasoline is less of an issue
Again portables are just as capable a lot cheaper, but not nearly as convenient.
The convenience factor allows for more usage. Especially more trivial usage. You don't hesitate to use genset because it requires absolutely no set up or user input other than pushing that button.