Think of thread and you usually think of lace and doilies and fancy delicate stuff. Traditionally, #10 cotton was used for heavy-duty stuff like bedspreads and potholders. Patterns for tablecloths often called for #20 thread, and you wouldn't waste your energy making fine lace and doilies out of anything chunkier than #30 thread.
A lot of patterns are very fancy, but I like fairly simple concepts -- they can feel like walking a labyrinth. Simple patterns (I do a lot with the basic granny square stitch) can have interesting optical effects.
At one point, I wondered if the number of loose ends on a small-scale motif project would drive me nuts:
Using the same thread, I could see the difference in gauge for different hooks on the same pattern:
I use it to try out new ideas, make prototypes, with a yarn that is small enough to be a purse project, and remarkably inexpensive. And since it is such an underrated material, you can get it even cheaper at the thrift store.
On top of that, because it is cotton thread, it isn’t fuzzy like a yarn, and it doesn’t split easily (unless you are using a hook that is too small). Having one sample of a motif can take the place of remembering where the written pattern is. ￼
It works with knitting, too. This is #10 thread in knitted seed stitch on #6 / 4mm needles. I really like how it turned out and am considering it for a window covering, like a sheer. It looked a bit more clunky in the double crochet portion (to the right), stitched with a 4mm hook.