Vegetto in the ToP

[Void]

Why do you think Kaioshin didn't mention having Goku and Vegeta fuse when Potara was allowed? If Vegetto got the same boost as Kefla and his base was at least on par with hers then he would've been unstoppable. SS2 Kefla is already UI tier so Blue Vegetto would've been far superior to that. Why do you think this was avoided?

 

[Pyro]

They figured it wouldn't be worth it. Vegetto lasted all of two minutes against Zamasu, and if he gets knocked out by Jiren (or defuses and Goku and Vegeta are low on energy), that's two good fighters gone.

 

[Papasmurf]

They ddin't even try to fuse again in the manga despite Gowasu still wearing a pair of earrings to offer them. I think it's unlikely they'll ever use Potara due to UI/Blue Evolution's strain.

 

[Let's Go Fearless!]

Like Pyro said, if Vegito somehow gets eliminated then two fighters of U7 gets eliminated as well. Plus, they already got the number advantage.