Do you mean the Standard wrap with the markings / rating / branding on them, or is there an overwrap?
The standard wrap is also there because the can is often connected to the negative pin
I once saw a video where someone said (while pointing to a bank of caps with overwrap & glued to each other)
that its done to reduce vibration while isolating vibration, because caps vibrate (oscillate) when they are working, which I already knew.
I think it was Ave, or Mr. Carlson, or Big Clive.... Idunno, It's a big tube out there.
Where are the pics?
Picture books are fun.
Those word books are yucky.