I like to spin for a specific project so I can choose the characteristics of the yarn I want. Here I'm spinning wool for socks, so I'm spinning a thin, firmly twisted thread. There's always a trade off between strength and softness - more spin makes a thread stronger, but less soft. So if I was spinning for a scarf, say, I might put less spin in, which would make the yarn softer than this thread, but less strong. There are other factors that affect how much spin you need to put in, such as the fibre being spun - cotton needs more spin to hold together than wool, for instance. In any case, the idea is to spin a yarn that is 'fit for purpose'!