I agree with #2 in Rozzie's post above. That's a huge factor for me. But only one of many.
For one example, I grow and freeze/dry/can a lot of our own food. The reasons:
1. Saves money.
2. Fresher, organic, healthier.
3. It's "green" for me to reuse containers year after year after year.
4. I enjoy it. It feels very rewarding, and we eat in luxury all year long.
For another example, making soap, my reasons are quite different:
1. I want to make money.
2. I enjoy homemade soap, and now my costs are covered.
3. It is NOT green, at all. The horror of the piles of recyclable oil/fat containers in my garbage reminds me that probably corporate America makes soap much more efficiently.
Some others (drying laundry on line) are purely economic. It does NOT feel nicer to wear clothes from the line compared to the drier
Others are ethical (raising chickens for meat and eggs).
Others are opportunistic (making yogurt, cheese, buttermilk and butter since husband helps on a dairy farm).
Yet others are about other things (having bees, since they are in crisis right now).
So, I imagine many people enjoy dabbling, but isn't that how a lot of us started? I certainly didn't begin everything all at once. Probably many reasons for many people. I expect some will drop off, others will stay.