They are basiclly for looks they are not essential.
jay
Actually, that's just why most folks now days get them (I've lusted over having a pair since the 70's just for the cool factor).
They're designed as editing aids (editing hubs).
When someone does lots of splicing and other tape editing it's essential to find the exact spots on the tape to splice out or in tape. Now this isn't so important to a hack like me who's happy with getting the splice "close enough" but someone who really knows what their doing (like a fellow around here by the name of Paul) is an artist when it comes to producing seamless splices and knowing just where to put them.
To edit tape you'd stop in the area to be edited and engage the "cue" switch which drops the tape lifters down allowing the tape to make contact with the heads. The rollers
aren't engaged since that would be the same as the
play function and the tape would move.
Now you need to find the exact spot you wish to splice. To do this you need to
jog the tape reels back and forth and listen. Without the editing hubs you'd have to move both reels by their flanges which certainly can be done, but it's much easier and precise with the editing hubs as
handles (especially if you have to go more than a tiny bit).
So, in reality, they're handles but it doesn't hurt that their very cool looking either.