The trouble with this is that, as a software author,
it doesn't really matter if it takes 70 seconds instead of 33 to install my software. 70 seconds is fast enough, for someone who's already decided to start downloading something as involved as Meteor; even if it took one second it wouldn't get me more users. And it would have to take over 5-10 minutes before I start losing users.
On the other hand, having to deal with support requests from users who don't have any decompressor other than gzip will cost me both users and my time. Some complicated "download this one if you have xz" or "here's how to install xz-utils on Debian, on RHEL, on ..." will definitely cost me users, compared to "if you're on a UNIXish system, run this command".
From a pure programming point of view, sure, xz is better. But there's nothing convincing me to make the engineering decision to adopt it. The practical benefits are unnoticeable, and the practical downsides are concrete.
On the other hand, having to deal with support requests from users who don't have any decompressor other than gzip will cost me both users and my time. Some complicated "download this one if you have xz" or "here's how to install xz-utils on Debian, on RHEL, on ..." will definitely cost me users, compared to "if you're on a UNIXish system, run this command".
From a pure programming point of view, sure, xz is better. But there's nothing convincing me to make the engineering decision to adopt it. The practical benefits are unnoticeable, and the practical downsides are concrete.