monotone is a versioning system, its main reason to be is to be used by developers to actually manage the history and not by users to get the nightly tarball... so, even tough it could certainly be an useful feature, what you want was not yet implemented. Of course many websites do provide nightly tarballs, but that has nothing much to do with the specific versionig system they're using anyways and more with some cron
script they have laying around (and those could be easily be done for monotone-hosted projects as well, even in realtime, using server-side hooks such as the one that updates monotone website itself as soon as a new revision is uploaded).
OTOH if you want a "real checkout" of an incomplete set of revisions (intended for a developer, not as a static tarball) what you want is a future feature which in monotone lingo is called partial pull.
If what you really meant is that, yes, you would like to have the history too, but was only trying to avoid that for performance reasons, that's a still different issue... and the main reason for that is that "mtn pull" (or the pull-part of "mtn sync") doesn't mean "I want to download stuff" but really means "I want to download stuff and cryptographically check every single bit of it so that I'm sure no untrusted data ever shows up in my local database" and, of course, cryptographically check every single bit needs some time... yes, a "pull without checking, I will do 'mtn check' later" could help here.
I do agree that, for a user that really only wants to download "an instant tarball" of current revision could be useful and, for a developer which is not much interested in past history, partial pull or "fast unchecked pull" could be an interesting features. Unfortunately, the monotone contributors didn't so far mange to write those features; any help is appreciated. ;-)