The idea is so you only need two long wires going from the power supply to the electronics boards. I'm sure I saw this done in a tutorial somewhere, but I can't for the life of me find the source. Also I just bought a kit and the build manual says to use four wires, but only two wires come with the kit, so I recalled that bit of advice in the tutorial and thought hmm either they shorted me those wires, or they just expect me to make do with two. Perhaps the jumping method is common practice? But then why have a plug on the ramps board with four inputs? Why not just two inputs and split it internally if need be?
I guess that the external split is at least partly done to force the user to utilize 4 wires. 16 Amps at 12 Volts is quite a bit of power and you don't want your wires or connectors to melt. If you use twice the wire cross section by using 4 instead of 2 wires, you also reduce the resistivity and hence heat created in the wire.
Put it the other way around: Using 2 instead of 4 wires raises the risk of your setup to catch fire.
Still, you can use that bridging technique, if you make sure that all your wire diameters are big enough.
I would advise you, however, to cut the wires that come with your kit in half and use the connectors in the way they were meant to. For optical appeal and less cable clutter you can still put the wires into some braided sleeve for example.