After beating every stage in the earlier games, you'll remember that you see the characters start appearing one by one at a certain place.
This was the original game's screen at the Gelateria:
Twisted and Touched had these too. The former at Club Sugar, and the latter in the Hawt House (with Vanessa, and she's there even when you finish Wario's first level).
But after Touched...these were kaput. That kinda blows. What would Smooth Moves' have looked like and where would it take place?
Maybe it could have taken place in the Temple of Form or what not, but that itself may be why such a scene wasn't present. Because they'd already had them in the Gelateria, Club Sugar and the Hawt House, and the relevant locations from later games didn't lend themself so well to the idea. DIY would have been interesting here, since apparently WarioWare split into two companies at that point. Would that have meant two hangout spot scenes would have been present?
Smooth Moves did have Wario run past everyone who had a stage previously, when he is chased by the Splunks in the Tiny Wario ending and Game & Wario did have everyone come together at Club Sugar, during the Captain Wario ending.
Obviously it's not quite the same as the ones that happened after every stage ending, but it's close enough.