From my experience at some airfields a lot of people seem to have the attitude of "well it was ok on the other flights with that much fuel, so it must be ok this time".
What, like "three adults, a small child, full fuel, no luggage is OK 'cos I did the sums once", but if the child wants to sit in the front I don't know what the balance will be so do a W&B, and for a larger fourth person or any luggage at all I do the W&B? Isn't this what everybody does?
Ok, so maybe the C152 will fly grossly over-weight, but put your new PPL holder in a PA28 or similar and then maybe weight calculations will be a whole lot more significant!
Yes, certainly the comments I made about an overweight C152 were specific to the C152.