Why are brake ferrules longer than shift ferrules? I'm having a lot of trouble finding short brake cable ferrules. The ones I've found are all long and tapered as in the picture below. 

I don't understand the purpose of this design. The brake housing only fills half the ferrule, so the cable is effectively rigid for an extra centimeter. The housing is also loose because all the ferrules I have in this style (various brands) measure 5.2mm internally on the female side. The tapered end is loose in the cable stops on my bike and doesn't fit my mountain V-brake shifters. 

What's the point? Why are the only short brake ferrules available the cheap crimp-style?
Stepped brake ferrules, the long type you mention, exist for using 5mm compressionless (aka braided) brake housing on levers and brakes that have a plain 5mm bore, intended to take conventional spiral brake housing without a ferrule, such as many brifters and road calipers. You must use some kind of thick-ended ferrule with compressionless brake housing, or else the wires will pull through, same as using compressionless shift housing without a ferrule. Using them elsewhere, such as housing stops, is basically incorrect.

If you want more premium 5mm ferrules than the commonly encountered plated ones, a couple companies make them, Wheels Mfg and Jagwire for example.