The important part...

There's an old ditty, something like "for want of a shoe the kingdom was lost" - there's more to it, but the point is, without good feet a horse is pretty worthless. So hoof care is very important. If you're going to ride on the back, you have to learn to care for the hoof.
Carrie is such a good boys' mom, she's tuned in to what makes a boy happy. She is also a great teacher, seizing those teaching moments as they happen. Max is determined to do all the horse care necessary - he loves to ride. So mom taught him how to pick up the foot safely, and how to pick out the - well, let's say debris - efficiently.

Of course being Max, he quickly moved on to independence. Picture this punk in about 10 years...
A large part of teaching is demonstrating, being the role model. Carrie is also determined. She wants the very best of care for her horses, and usually that means doing it yourself. So she is learning to do a little more advanced hoof care, by rasping off excess hoof wall and keeping the hoof properly shaped inbetween farrier visits for trims. Neither horse needs shoeing, they have good feet and aren't ridden on rough rocky ground.
Which is a good thing. I wouldn't want to see Max turn his hammer-and-nailing skills to putting on horse shoes.... his quick little mind picks up things way too fast. Just by watching, he figures out how to do a thing by himself. And proceeds to do it.

One description for Max, in a previous post, was "Irrisistable." This post, it's "Determined."