Why Is The IP Boost Ranked Flex Only?

It's because Riot wants people to play their new Flex queue instead of solo/duo queue so they say "hey we will give you something extra if you accept our new idea."

They are worried it'll die if they don't incentivize it. And it's still the way they think the game should be played. They also don't care about normals. Just look at their removal of normal draft in most regions if you doubt me.

Don't worry, once they remove Normal Draft on your server you'll have no choice.

Play it like normals. Except maybe actually try. But try to enjoy the game foremostm

Is it? I saw the indicator while queuing for Blind Pick and ARAM yesterday (but I wasn't paying too close attention to it).