In Rust you're allowed to look at values without consuming them, which pure linear typing doesn't support (it requires exactly one producer and exactly one consumer).

Also, in my experience, most Rust programs tend to stash stuff in reference-counted boxes whenever calculating lifetime gets complex; which is reasonable enough (C++ does the same thing), but it is basically garbage collection, and I'd like to find an expressive, functional, non-GCd language which doesn't require this.