step down 5v

Does anybody know why additional Electronic components are required for the AC/DC Hi-Link Enclosed Modular Devices? I mean, the reason you use such A devices is to avoid having to add more Components. Fuses I understand. Just not the Capacitors, Resistors, Coil and so on. See pic below.

Hello everyone ! I'm planning to buy a 30w solar panel to attach to my two redundant powerbanks that will be constantly powering my rasberry pi which will be connected to the internet too. Such project I would use to plan building a drone too... I think that would be cool. I have a doubt...