Babies grow up.
And usually, they really need less supervision once grown up. At least, us SAHMs don't have to hover over them anymore, nor take them to and fro places. Which is why it is really good to have some sort of sideline to occupy you (and contribute to the family income). I also understand why some mothers start going to nursing vocational colleges or training for culinary arts, massage therapy and other possible income-generating skills. The bakers can sell their goodies as fast as hotcakes with the right pictures and rates at multiply. Some go into party planning instead, after mastering several rounds of birthday parties.
Some I know master photography and become professionals. Usually, these new careers are offshoots of mothering but some do return to their former industries.
Some further elevate mothering into a new level, that of full-time mentor through homeschooling. Hopefully, I am really up to the challenge. In any case, I am doing my best to follow what the homeschooling moms have advised me to do: to enjoy my son right now since he is really too young for structured learning.