Touchpad is very useful as an extra set of buttons.
In training mode in fighting games for example, pressing the left, middle or right side of the touchpad will spawn the training dummy in the left corner, middle of the stage (default start position) or right corner.
You can do this by going through a bunch of menus, but this makes it a lot less of a hassle.
Plenty of other games use the touchpad as an extra button as well. Bloodstained and Code Vein have it tied to the map, etc.
As for the light bar, I've never used it, but it makes sense for PSVR.
I just really wish they let us turn it OFF this time.
It just drained the battery for no reason.
Then just take it away and put buttons on its place.
If it's a touchpad it should be used as such.
They could change it for a touchscreen to display some menus, minimaps, and other stuff to make the hubs less intrusive, too.
But having a massive square in the middle of the controller to serve just as a button doesn't give it a reason to be there.