Did you even watch the show my dude
Half of the entire show was always about how Gohan had mad hidden power, from when he hit Raditz to when Supreme Kai unlocked his shyt, Gohan always had mad power on the low. Even 16 himself said "I know you have the power Gohan my sensors caught it." It's called hidden power for a reason pleghboii.
They don't even do that all the time, half the time they deflect blasts that are that weak. But that's not even really the reason why. If someone throws a pebble at you you know it's not going to do serious damage, but you'll still try to block it so you don't have to deal with the minor nuisance.
Dude, you are acting as if power levels are consistent and static. You gotta understand something about DBZ.... POWER LEVELS ARE BULLshyt. The ENTIRE reason they were even introduced into the series, were to show how inconsistent they are and how unreliable it is to judge a person's ability by their presentation. Don't judge a book by its cover, basically.
What someone's power level is, is NOT definitive of their overall ability or combat effectiveness. If anything the Piccolo/17 fight showed this as clear as any fight in the series.
If Superman's character was in the DBZ series, he'd measure at a low power level UNTIL he decided to up his strength levels, which does at nearly will. Superman is a broken character, he wouldn't even fit in the DBZ universe.