No, you don't. If you don't boondock, you don't need one at all, and for "very little" boondocking, you can almost certainly get by. I almost exclusively boondock, and I've only recently acquired a small inverter for the likes of small chargers that for one reason or another won't work off of 12 volt
. You will be surprised by how self-sufficient these trailers are!
Now, if you just can't get by without a hair dryer, electric coffee pot, microwave, vacuum cleaner, etc. for just a few days, then and only then had you better stay where there is shore power or carry a generator ... or maybe a much expanded battery bank and an inverter.