Teardown experts iFixit have got to the bottom of the Mac Studio and the state of its upgradability. The website has also investigated the Studio Display, which shares a few similarities with the 24-inch iMac.
https://www.notebookcheck.net/iFixit-clarifies-Mac-Studio-upgrade-potential-as-it-also-tears-down-Studio-Display.609850.0.html
The reason is very simple - to save money. That's the typical reason for skipping chips and leaving empty spaces on a board. It's a competition between saving money by not soldering what is not needed and saving money by simplifying logistics through fewer variants of a board. They have no intention of making it user-upgradeable.
"Currently, it is unclear why the Mac Studio has this limitation." - Really? You don't know? Its so that they can screw you over. Einstein!
"Currently, it is unclear why the Mac Studio has this limitation."
Upselling to i$heep while driving away cost-sensitive endconsumers.