I often think this as well, however I take the continual attempts at nearly every possible turn to syphon yet more personal info as a sign at least someone doesn't have it yet and wants it and maybe I can stop them getting it and also I think these operations that suck up and sell or otherwise exploit your data need a continuous flow rather than simply a finite set.

What they have is probably useful but actually to a certain extent it probably isn't of much use without more data constantly coming in. Organisations like Google or Facebook would have such a large proportion of the planet represented in some form in their databases that it that were enough it'd basically be mission accomplished and they'd have no growth opportunities. I can probably never really know, but it looks like they need you to keep interacting with their services to maintain useful profiles of you and the rest of their hoardes and if they didn't get it your data would be essentially stale at after time.