My perspective on these issues is slightly different from the rest of you because I am older (61) and my youngest is in college so I am no longer involved in child care but I remember it all too well. I am a single parent, having adopted my oldest son and taken in my younger two as foster kids (who ended up living with me permanently) so I had to learn how to fit my drawing into their schedules. I have lots and lots of sketches of track meets and ski meets (as well as having learned how to write sermons while sitting in my car between races.) My main problem in those years was finishing stuff because you can't do that in the bleachers of a sporting event! I tried all kinds of strategies and the only thing that ever worked for me without fail that I still use today is accountability. If I knew someone was waiting to see what I had produced, it made me figure out how to find the time even if the floors didn't get vacuumed that week I also taught my kids to do their own laundry from the time they were 8 years old, and learned not to stress out about their messy rooms. (OK, kind of learned.) I really had to develop a certain amount of selfishness which is really hard in today's child-centered climate but my kids all turned out to be great human beings and when they went to college, were quite proud of the life skills I had forced on them.
And getting back to the "Why" exercise, in a sense, that willingness to be selfish with my time and devote it to creative work that benefits no one but myself continues to be at the base of my struggle.