Even if you upload your videos elsewhere, YouTube is the place that everyone seems to expect them to be placed. Many sites make it very easy to add your video and will take care of all the behind the scenes technical stuff, leaving you free to get on with your life.
Which means that it makes sense YouTube to MP3 audio to create your videos with YouTube in mind.
Fortunately, that's reasonably easy. Part of the reason they've become as successful as they have is that everything has been made as easy as possible.