Of course it's beneficial! The idea of the sealer is that it takes all the wear & tear, then you strip it off and start again. In theory the actual surface of the vinyl stays intact, so the floor last much longer and looks much better whilst it is lasting longer.
In practice however, vinyl floors always suffer scrapes and scratches which go through the sealer, but a sealed floor will always outlast an unsealed floor. Considering the cost of installing it, paying a little more money now and then to haver it sealed is very cost effective.
And incidentally exactly the same principle applies to protector, definitely not a con and not a waste of time/money
