Any time I read one of those articles about working moms, some nice interviewee mentions that she likes how her job challenges her. The implication would be, of course, that her day care fodder is not so challenging.
Young children are not intellectually stimulating. They only know what you teach them, and even if you commit yourself to bringing them up to speed they get real balky when it comes to epistemology.
But it's plain silly to say that taking care of children is not challenging. Once I tried an experiment to see how long it would take for my toddler to get tired of playing "This Little Piggy." It was too challenging. I never found out. I am constantly challenged to get the clean clothes put back in the drawers before another three days' worth of laundry is piled up where the basket would be if I had gotten that clean clothes thing taken care of. I have to think of what to feed everybody--preferably something healthy, economical, and palatable to numerous people--and then go on to cook it every single day. Most challenging of all, I have to try to get myself to do things that I could probably get away with not doing.
Are my days filled with simple, mundane tasks that anyone who made it out of sixth grade is capable of handling? Yes. But that doesn't mean they're not challenging. And here, I'm finally getting to the point: the truly challenging thing about them is that they are not fun and not impressive. They are not things that anyone wants to do because they require you to quit thinking you're too smart for this and get your hands dirty and get no respect for it. They are not a challenge to ability, but a challenge to pride. I'm in much greater need of the latter.