For a commercial, a YouTube video, whiteboard, etc., if the music bed -- or background music, if you prefer -- doesn't match what's being said (or seen), it detracts from the piece.
As such, I often spend a lot more time looking for music for a commercial than I do voicing the commercial. A 30-second spot, for example, might take 5 minutes to record, re-record, re-record that one part again, and then edit. But finding music for that spot? Might take 30 minutes. Maybe more.
So I'd rather not do it.
Now you could, if you were cynical, call that laziness on my part. I prefer to refer to it as an effort towards efficiency. I could record six commercials in the time it takes to find one music bed. And since it's my voice I'm selling, it makes sense to avoid music beds.
But the guys from Did You Know really wanted music. So my deal with them is to add music to the voiceovers I do for them. This is further complicated due to the length of the pieces. The last one I did for them was 6:40. I needed TWO music beds (and had to loop one of them) just to make it work.
So? Did it work? A couple comments on the YouTube video would suggest it didn't. Personally, I liked it.
I also found that I really like the musical style of Kevin MacLeod who created both beds I used: Deep Noise and Chee Zee Jungle - Primal Drive and offered them for use under a Creative Commons Attribution license.