As someone with 3 fellowships that all changed from casual spire to weekly Gold Spire in the last 2 months, I can tell you that the last chance at moonstone sets and a shot at the coveted phoenix artifacts were a HUGE motivator for those who didn't do full spires weekly.
Sure FOMO works, but what if there was no FOMO?
And who knows this FOMO moment might lead to a permanent gold fellowship.
Also casual fellowship, if you play in it? is it really casual, or is it what you consider casual?
Phoenix and bears are money makers and the game designers arent stupid and know this, but the way to capitalise on it is to make it "rare" and create and intentional shortage.
The moment you do get the ability thats when people thow away rationale and you can rake in the cold hard cash.
But thats with our type of players, but casuals? the fact that your "casual" fellowship went all out to gold for a phoenix artefact already means they are closer to us than to casual.
They are now also shows they "other" benefits the spire might have and that might create a higher participation rate.
This leaves the real casuals, players who just play the game there way, spend the money there wat and do not give a crap about effective towns, tournaments, spires and whatever. they just want a pretty town and a nice way to spend there time and money.
They see somthing and go like ok, I want that, where can I het it? thats how they might be introduced to the spire.
and since there "casual" and not really grasping the how it works, they most likely spend more money in the spire then they get out of it.
How many times have we seen on forum players post I spend a ton of diamonds on extra turns? how to solve it 5 options 3 turns. that doesnt fit.