It takes no genius to note that even on the back of the packaging for this product there are the words: "Unusual Emergency accessories."
Obviously this gift is a novelty, unless there is desperately an emergency that calls for the use of a vibrator with batteries not included (at least you're getting the heads up, imagine if someone received this and needed it in an emergency, like to fight off next door's cat, or appreciate Ryan Gosling, only to find there was no batteries).
An ideal hen party gift (which is what I'm using this on, re-usable gifts are great...WAIT, NOT IN THAT WAY*) which is bound to create some sort of laughter one way or another, be it through comparisons or general humour, maybe not best that you give it to your mum for her birthday though.