Since Lord Guru’s passing, the Namekian Dragon Ball’s have also seen some slight improvements as well. However, one thing that was never interfered with was the fact that the user of the Dragon Ball’s had to wait a certain period of time before they could make another wish, as the Dragon Ball’s turned to stone after the dragon was summoned.
It’s possible that the reason Earth’s and the Namekian’s Dragon Ball’s maintained this feature is due to lost information, which for some reason, remained unknown after the Namekian’s travelled while escaping their dimension. It could also be an ideological choice, as some Namekian’s may have felt over usage of Dragon Ball’s could be dangerous and included a cooling off period.
Over the centuries and after the race spread further out into their new dimension, it’s possible some Namekian’s misunderstood their pre-dimensional switch ancestors instructions for Dragon Ball’s. Theory may have been mistaken for fact and as a result, a time-period between wishes was though to be required. However, if the current Namekian’s on Earth or on Planet Namek learn of this lost feature, then they should be able to adjust their Dragon Ball’s to include it too.