I for one would not be comfortable using a can of fix a flat on my RV.
1. I don't know enough about tire damage to know if it was appropriate to use it or not for a given instance;
2. I don't think fix a flat was necessarily created to plug a leak under the weight pressure of an RV versus a sedan, and I would worry that it wouldn't hold up under the weight until I made it to the tire shop - instead leaving me stranded on the side of a road instead of in my driveway or work parking lot;
3. I have dually rear tires and don't have the extended tubes. That means I have a good chance of not being able to reach the flat without removing a tire and I'd rather pay someone to do that, then do it myself.
It's really not difficult to understand that people have different comfort levels when it comes to DIY repairs/fixes. There are many things I will do myself (including replacing a gas wall heater), but other things, I'd rather pay not to do them. Laziness and/or a desire to complain don't really have anything to do with it.