It's cool to see this here, thanks for posting! I remember working with SimpleDB when taking a a database internals class. It was an interesting and engaging way to learn concepts like strict two-phase locking and Selinger-style query optimization.
Yeah, I think its a shame that most teachers don't give assignments like this that tie the big picture together with the low-level details. After students complete a big assignment like SimpleDB, they'll have a working artifact that they can reference for the rest of their career
I think the main issue that universities face is time. There is only so much time in each semester and, as we all know, building and improving on a database is a lifelong task.