AnderMost likely because they're 3rd party keycap sets that aren't produced by KDB, in the same way they don't produce the switches or LEDs themselves. When more generic keycap sets are sold they usually come in full sets of 104 keys (and sometimes even more, to cover the full spectrum of common non-standard keys). It's really only high-end custom keycap sets that you can buy in parts (and have to buy in parts, actually) such as alphas, modifiers, numpad, etc. They're including options for people who don't have keycap sets they can add on already. don't want to spend a lot of money on a high-end custom set, or just want an all inclusive package. So they include options of more mass-produced sets that are generally available at any time rather than the sets you see on Massdrop by a specific maker.