Too many people are buying the cheap one! Force then to spend more on the expensive version and use the 3s as an anchoring point so consumers are more likely to just get the upgraded one!!! - Shareholders
So you'll now be sacrificing features instead of just storage space if you're looking to save some money by buying the smaller one
Cheap - 3S 128 gb -$300 (Q3 128 is $430)
Mid tier -3S 256gb - $400
"Premium" - Quest 3 512gb $650
Microsoft did the same thing when they phased out the "Middle" Pro 360 model, leaving only the crappy arcade and the most expensive Elite SKUs left