Let's not get nasty.
I have a built in inverter and have used it to charge up my phone battery. I am not the type that needs a plug in coffee maker or a toaster. I don't watch that much television either. If I did use my inverter more I would have to change a few things.
First of all, there are the two batteries I have to maintain. Using an inverter a lot draws these down. To charge them I have to run my generator. Why not just turn on the generator and avoid the inverter? The answer is people want to run things late at night when a generator would be an issue. OK, run the appliances late into the night and draw the batteries down. But how far down will they go? It is not good to discharge your house batteries below 50% I have been told.
Secondly, if I did use the inverter a lot I would need to upgrade to some solar power and/or more or better batteries. These options are good ones an I am guessing that proponents of inverter use have done this.
So, don't classify me as "old school". While I am old, I am also open to new technologies. Affordability does come into play and I do recognize that as an issue. The OP asked a good question. Like all things in the trailering world, there are many ways to find your comfort zone.