Why doesn't Riot cross-promote game stuff at eSports events?

To be clear, I'm not whining, I'm just curious about this!

On its face, it seems like these big eSports events like Worlds, All-Stars, etc. would be good platforms to announce whatever new/cool things Riot has been working on (like the latest champion or special event). It certainly seems like if Riot ended the Worlds broadcast with a Harrowing announcement (for example), it would probably cause a big group of people to log on, and help turn the "worlds!" excitement into excitement for playing the game.

Now, I could see Riot wanting to keep eSports and game marketing separate to make the broadcast seem more journalistically legitimate. But they do advertise in-game stuff on the broadcast (for example, mentioning Championship Shyvana/bundle on the preview show and repeatedly on the bottom scroller). So that probably isn't the reason.

I'm sure there is a good reason, but I can't think of what it is. Any ideas? (or insight from Rioters?)