Because they are convenient for lots of routine tasks.
> And why have they taught their kids to use them?
If they are in a house with kids, the kids don't need to be actively taught to start using them.
> I feel like we're on the verge of an age where every single person is used to, and just has an Alexa/google home voice assist in their house.
Pretty close, yeah.
> Not only is it unnecessary
Unless you are dirt poor, chances are most of the things you have and use are unnecessary.
> but as you can see from thia tweet, they're never going to be perfect.
This tweet tells how they are (well, Alexa is) now, not what they will (n)ever be. But, yes, nothing is ever perfect. Clothes dryers are both unnecessary and imperfect, and kill people every year: are you going to go on a crusade against them, next?