Ladies (and gent), it was primarily due to convenience (as I have several scattered around the workshop/house) and trying to utilise my laser that's been sitting relatively idle for nigh on 10 years.
A box was my first thought, but then that'd be inconveniently "drawered"... under bench/shelf mount made the slide out easy access and "hide".
JMcI, some were stained (Feast Watson)... I'm past making stuff in the workshop pretty-pretty... here in downtown Churchill, our "exotic timber" is MDF and/or melamine... anything else is gold... so my scrap bin is my "super exotics" reserved for those special occasions.
The black ones were mainly for up in the house where the colour theme (from past owner) is black and I'm not much for change so it stayed black.... and rather than pour the decanted stain back in the can, I got carried away with some of the cases... and love the smell of metho.
If your first cut is too short... Take the second cut from the longer end... LBD