Actually, this comes from Uli's slavish copying of the Moog spec. The original Moog modules that made up the System 15/35/55 module complements never had buffered mults...NOR do they have inputs that have the right sort of circuitry that allows you to avoid using buffered mults. This is just one endemic-to-Moog issue that later manufacturers (starting with ARP) dodged.
Another great example is Moog's shitty S-trig system. Yeah, you heard me right...shitty! See, S-trig stands for "shorting trigger"; there's a trigger bus that has a constant +5V on it, and when you trigger something, that +5V drops to 0V because the bus has been "shorted" to ground. BUT...and this is actually important when considering Moog modular stuff (which in essence, this is, at least as far as basic design conventions), if you put too many devices on the S-trig bus, it'll cause the bus's voltage to sag (because, as noted, Moog modular stuff has NO buffering on inputs), and when that sag hits somewhere in the +2-3V range, the S-trig will suddenly get a mind of its own and random trigger-fires will start happening. To say that this is irritating is an understatement!
I'm sure that Uli could've one-upped the Moog designs by adding front-end buffer circuits where needed. He didn't, though. And getting rid of the S-trig was one thing that I KNOW a lot of us who've used the originals wanted...and didn't get.