Then you don't need one.
You only need one if you want to run AC devices while not plugged into shore power. This will typically be people who boondock or people who want their residential fridge to stay on while not plugged in.
For people like me it is mandatory. I am rarely plugged in and the times I am, it is typically too low amp (15amp) outlet. The inverter also provides a buffer of never losing power and not having to do things like reset microwave clocks.
2014 Volvo 630 Tandem 2016 Chevy 3500 DRW, crew cab
2016 Fuzion 325T
675ah AGM, MSH 3012 inverter, 960w Solar