I'm making a champion concept, and it includes a passive that I don't want abused in the early game, so I stuck it onto the ultimate (so that it scales at levels 6/11/16, just like Ryze.) After browsing the wiki, I found that some passives (like Karma's) scale at levels 1/7/13 instead.
Why do some passives scale at levels 1/7/13 while others scale at levels 6/11/16?
I would guess for balance. At levels 6,11,16 you get your ult and an ult up. So if you get your passive at the same time the damage/utility would be overwhelming. You get the passive scaling 1 level later to make levels 6,11,16 less oppressive. For example you might be level 6 and have ult plus passive scaling vs a level 5 then he is really behind, but if your level 7 and your opponents 5 your just winning lane hard. This makes 1 level when enemy is almost the same level less oppressive.
Among other things, it indicates different numbers of shifts. A passive that scales at 1/7/13 has 2 shifts (base at 1, shift at 7, and shift at 13). A passive that scales at 1/6/11/16 has 3 shifts (base at 1, shift at 6, shift at 11, shift at 16). This allows for the power growth to be more gradual.
