- They are not cashgrabs
Unlike TFT, modes like Nexus Blitz fail to implement a moneymaker-mechanic that requires you to spend to gain cosmetics that should be basic products. If it doesn't sell, then they don't care how popular it was.
- It is not SR
Simple as that. They aren't a ranked map you can broadcast and charge fees to watch it. Summoners Rift is the only map you will ever see in worlds.
- It's an inevitability in Riot's Focus plan.
They removed Dominion and now they remove TT. Someday in just another 2-4 years they will remove Aram too. In their own sense, it's hypocritical to introduce new gamemodes if you are trying to minimize them until only 1 is left.
It's really simple. Riot is worse than EA cuz EA at least **SOMEWHAT** listens to their community. Riot couldn't care less if we all died in hellfire as long as they get our cash.
Edit: had to highlight the word Somewhat because some people can't really read.