Alef actually has/had real tuples, as does Limbo.

Looking at Alef, apart from using tuples to provide multiple return values in a C-like language, they don't seem to actually add much functionality over what Go has without them. One of the few extra things is the ability to pass a tuple over a channel, however passing a struct is more or less equivalent.

I've not looked in much detail at what Limbo could do with its tuples.

So maybe they don't really add that much, hence why they were not carried over when Go was created?

Alef had enums, Limbo has something like the Go constant scheme and iota. Limbo also had tagged unions / varient-records, in a sort of Pascal like fashion - the "pick adt".