Masteries & Runepages limit promote meta
it's a question that I have been asking myself lately. You can play every role on multiplay ways right:
- Support: Melee & Range (if you don't calculate the sub groups Tank, Sustain & Poke) => 3
- Adc: AA Caster & AA AD => 2
- Mid: All (pref Mage, Assassin) => 2
- Top: All (pref Mage, Fighter/Tank) => 2
- Jungle: Supposed to be 4 ways => 4
Let's say you use the following champions: 
Every champion on this list will have a different runepage with a possible exeption on the adc's. This makes up for 12 runepages in order to have a stable set available. This means you will have 8 more runepages available that are required for different matchups or when you want another champion in your team that would require a different runepage.
But but than let's see what lanes would need a special runepage change against a specific matchup:
- Mid: Mage vs AP (often default), Mage vs AD, Assassin vs AP (often default), Assassin vs AD ==> + 3 runepages
- Top: Mage vs AD (often default), Mage vs AP, Fighter/Tank vs AP, Fighter/Tank vs AD ==> + 3 runepages (since top mages often are bound to a different runepage setup)
- Jungle: N/A ==> +0
If you count this together whe only have 2 runepages left!!
So basicly you will have to use 18 of the 20 from your runepages in order to have a champion available for every possible role league can give you. That's pretty f*ckup if you ask me since this limits build testing & champion pool by a hugh amount. This is also the reason why whe always see someone that can't play a specific role. Since in order to make room to go out the meta you will have to remove a page that you needed to play that role.
But that's not the worse part. That champion can be banned when you play ranked. This makes the risk of learning all roles even more difficult.
