My reason for carrying a battery charger is I use it from time to time for cars that won't start.... Occasionally it's even my car.
Now mine is an old "Dumb" charger,, (But I provide the smarts so that's ok) But I recall in a parking lot not all that long ago my wife (now my late wife) was shopping and some folks were looking forlorn so I broke out the 100' cord and the booster/charger and after a bit of work got 'em going.. Sent them to the nearby auto store that also installs batteries. Cause my suspicion is they needed one.
The new towed I bought to replace the one my wife totaled when she died.... Well the battery lasted about 2 months and I had to boost it to get to the battery store as well. Major pain in ye old anatomy. But a side effect is I adapted and hooked up the old towed charge leads so I can plug an anderson extension cord in between RV and Towed, No matter if Towed is in front or behind RV. (or beside it on the service side) One of these days I'll add an anderson pair to the generator as well.