★★ ʜᴀᴋᴀɪ ★★
Early on in Dragon Ball Z, Gohan became a prime target. Unleashing his Saiyan power against Raditz, Piccolo decided it would be a good idea to train him so they would have more power on their side when Vegeta and Nappa showed up to Earth. The first time we see Gohan entering the battlefield was against Nappa. His presence not being there likely would have cost some time for Goku to arrive in time.
What do you think would have happened had Piccolo never trained Gohan?