That's just it: Goku has always been willing to learn from others, while Vegeta never wants to listen to anyone -- he already thinks he knows it all. That is likely why Goku tends to reach these pinnacles of power before Vegeta. Tbh, that difference alone speaks volumes about their wildly opposite personalities. mmm
On a related note: imagine if Goku had never learned IT..? That technique has become FAR more useful than Toriyama probably ever intended. He uses it all the time now.