it is expected as they are moving from LESS to SASS.
> "Moved from Less to Sass. Bootstrap now compiles faster than ever thanks to Libsass, and we join an increasingly large community of Sass developers."
That said, the major CSS frameworks that I am familiar with (Foundation, Bootstrap, Bourbon, etc) all seem to be choosing SASS, so it feels like it is becoming the de-facto standard..
I'm sure there are lots of excellent and well-supported products that still use LESS though.