I knit a lot of things that don't really need a swatch or that are easier to start knitting and then check and see how it's going (socks for example).
Unless fit is crucial or I am totally unfamiliar with the yarn, I tend to be able to get a fairly good idea how something will come out. If I'm knitting for kids, I usually make it a size larger anyway for them to grow into.
However, if I'm knitting something like the project I'm about to start, I will do the swatch and wash. It's a yarn and fiber blend I haven't used before (so I'm not comfortable on how it will react). It's a pattern where fit matters (Eris). This will be my first swatch in two years
I avoid it when possible, and do it absolutely by the book when I think it's really needed.