Dragon Ball: Why did Goku & Vegeta not fuse in the Tournament of Power?

With the imminent return of Dragon Ball Super, many fans have taken this hiatus as an opportunity to reread the series from cover-to-cover.

Dragon Ball Super Goku vs Zamasu Fusion Chapter 25 by Amanomoon on DeviantArt

Dragon Ball Z: Season 9 - DVD

Dragon Ball: Why did Goku & Vegeta not fuse in the Tournament of Power?

𝙏𝙝𝙚 𝙣𝙚𝙬 𝙨𝙦𝙪𝙖𝙙 𝙖𝙩 𝙩𝙝𝙚 𝙣𝙚𝙭𝙩 - Dragon Ball Exclusives

List of Dragon Ball characters - Wikipedia

Universe 7 ready to win the next tournament of power in half an episode (art by @Fellipart) : r/dbz

Dragon Ball Z: Fusion Reborn - Wikipedia

Dragon Ball Super Goku vs Zamasu Fusion Chapter 25 by Amanomoon on DeviantArt

Gogeta, Dragon Ball Wiki