You should be monitoring progress and prepare to abort take-offs is things are not going as planned but I would doubt many do a W&B or take-off performance calculation.
Interesting observation. One would hope you were wrong...
The sad part is that such misbehavior is highly contageous. "Yeah, I know we were taught to do that, and the law even says we must, but nobody else does so I won't either..."
I would put it this way: Most pilots (non-professionals in particular) are not terribly good at what they are doing. If we fly the way everyone else flies we won't be very good either. Then again, one doesn't have to be the best pilot in the world in order to be 'sufficiently safe'...
I think being a good pilot is a goal in itself, whether 'necessary' or not. So I do those calculations every time. I rather enjoy it too.
We are all very good at it when students, but bad habits do creep in over time.
Isn't that the truth! Experience is a prerequisite for both complacency and excellence, but only the former comes automatically.