If Scheme is so good why MIT drops it?

[Paul Rubin]

Carl Banks <pavlovevidence at gmail.com> writes:
> Wrong.  It only partially undermines the utility of native threads,
> not completely.  Native threading allows some threads to run while
> others are blocked in a system call (as well as in a few other minor
> cases), which can't be done with green threads.

Why is that such an advantage?  Green threads work fine if you just
organize the i/o system to never block.