Why does Kayle's E apply Spell Effects and Kog's W doesn't?

This has always puzzled me to no end. Both skills do effectively the same thing. Active skills that boost attack range and grant OnHit magic damage. But Kayle's applies spell effects and Kog's doesn't. The distinction is almost wholly irrelevant unless you're playing AP Kog or what have you, but it seems like an odd inconsistency in how otherwise very similar abilities work.