if franky punched kizaru we'd just see admiral slander across 54000 new threads. he introduces stuff so it can be used later, or sometimes just to world build. it took a long time for the tamate box to come back around too.
Oda's been hyping up this concept a lot, actually.
Gear 5 Luffy grabbing Lightning vs Kaido.
The Holograms/Hologram gloves in Egghead.
Now we have Rainbows that you can create/ride.
Hologram technology is clearly going to be big at some point. Imagine Holograms that can be turned "off and on" in terms of tangibility? Making it so the Hologram only exists physically when the controller wants it to? That would be very dangerous tech.