A Wizard is an Engineer. He puts pen to paper. His spells are blueprints, he pieces them together carefully, ensuring each gesture is in its exact place at the right time to draw forth their power.
A Sorcerer is an Artist. She puts brush to canvas. Her spells are paintings. She flows wildly through her spells, letting intuition and feeling take over, creating something beautiful and potent in the process.
They both use components, they both cast magic from the same source, but with different methods.
All of these robes are,
, MAGIC. There is no reason that a wizard couldn't get spell slots from a robe, or meta-magic feats. There is just an odd discrepancy in gear that leans towards certain classes, much how like years ago we had over a dozen magical scimitars, a dozen short swords, and ONE Two-bladed sword (also like, one sickle).
Good new items need to be made to close the gap, or new versions that aren't arbitrarily restricted by class.
Get that creativity going, make some items!