I don't think that trailhead weighing is just for bragging rights or fun, nor to make any frantic last minute gear changes. Well, maybe some of the more blatant ones; I once hiked with a fellow that carried a big cast iron frying pan, pulled whole potatos out of his pack, a big package of bacon … I might have tried to talk him out of that had the scale turned up something alarming.
For me it's a good reality check — if the weight is very far off what my spreadsheet predicted, then it's something to think about post-trip. A right-at-the-end-of-trip weighing is of course helpful too, along with an estimate of how much water was in/on the pack before and after.
If my wife and I are on a trip together and the weights are too disparate, then maybe a little more "communal gear" makes its way onto my pack.
I don't have a hook-scale; sounds like something fun, but rather than buying something new I toss in a square of 3/4" plywood and a bathroom scale. The plywood gives a sufficiently flat and stable base for the scale to sit on at the trailhead.