I would honestly say that people might use 10 different spell types at most, even if a lot of them are great, it’s a LOT of spells to swap between. The average person might find it too much of a headache to try and personalize 24 moves for EVERY situation on multiple types of magics whilst also factoring in synergies- they’ll likely stick to 2-3 strong combos and or a few good solo moves.
Of course there will always be people who want to collect rare spells like collectible cards for fun.
Main reason is probably since tornados fling you up, but it’s also good for Gale Potions, future Water Spouts, future Dark Skies (if they get added), and whatever else will fling you like Wind Mage