Why do bipolar electrolytic caps have a long and short lead?
Apart from using standard machine setup for polarized and non-polarized, the different lead lengths aid manual insertion.

The long wires will seldom be exactly parallel making it tricky to align both simultaneously. Having different lengths means that one can be inserted and the other aligned by pulling on the body of the capacitor.



Figure 1. Nixie tubes. Source Vannadiy on eBay.

A similar trick can be used to insert a nixie tube into a PCB where, otherwise, trying to align eleven pins at once would risk loosing one's sanity. A chosen lead is left at full length and working around the tube each wire is shortened by a mm or two. Now insertion becomes a mater of engaging each wire, one at a time. The wires are cut to length after a couple of solder tacks to keep the tube in place. I think I first read of the technique in Elektor magazine.