The screen and speakers are actually pretty awesome for the device size, and I appreciate that the controller is right there so I don't have to deal with propping anything up or linking a bluetooth device.
I bought it because I have my PS5 in a dedicated room I'm rarely in with the family around, so I could keep it in there on the big screen but still play it and be somewhat present at the house when they were watching something I was less interested in.
However, Like hph said, it's absolutely unnecessary and a total luxury item.