Mine is anxiety more then anything, to be honest.
I always wanted to sew by machine, my mom was one that to learn to sew you have to do it by hand only and it turned me off of it for a long time because I couldn't do it fast and I didn't know how. When we moved to Texas from Oklahoma, hand sewing was a way for my great grandmother to get to know me and spend time with me (and she was actually quite talented at hand sewing, far more then machining) and my grandmother was a tailor. I learned to actually hand sew through the Women's Institute of Domestic Arts and Science course (both of them had copies of it...Great g-ma the 1918 version, Gma the 40s) with my great grandma when I was 10 over about a year, and the chart you see if from an old book (they had several versions of this) and was like, THIS is what you need to work to get to speed. Machine, hand...here's the times, work to them.
It didn't hurt that they used my perfectionism and having a natural talent at it to help me get good. The chart was actually a great motivator...the first things I hand sewn were horrid on times (an apron took me 10 hours, and drawers took about 12). I didn't actually hit those times until I was in my 30s, and I don't always hit them now; a plain apron takes me 2h12m on average...but it's not always "plain" in the 1866 sense of the garment (which is when this chart was published).
By the time I was 12, I made extra money hand sewing hems for men's suit pants for my grandmother (my great grandmother died shortly after my 13th birthday). Not much, and certainly not what she got paid for it, but a couple bucks. Last thing I did with her before she got cancer was pad stitching a men's coat for tailoring...she died before I got good at any real form of sewing.
I make at least one garment a year by hand completely, on purpose. And not aprons or lingerie (I make aprons by hand to ignore my in laws when I have to go and fine lingerie often works out with better control by hand and often make a dozen or so a year of them) but something like a shirt or dress. It just reinforces what I know. And to be honest, you can always find a needle and thread but a machine may not always be around.
I also get into weird tangents. I made a dress of deer skin out of bone needles and sinew to mimic the c. 700 leather dress found in a burial tomb and one of my ex husbands made me a set of iron needles that have no real use in modern sewing, but I occasionally use them for the sheer fun of it.