I tie a little and buy a lot. Honestly, in a sense, I see fly fishing and fly tying as two different hobbies. Yes, there is a strong relationship. One could apply the same to rod building, furled leader making, streamside entomology, and more.
A person can only have so many hobbies before it ends up being you are spreading yourself too thin (not being retired, that is a smaller number than some others!). I do consider both to be my hobbies, along with guitar playing, ham radio, voracious reading, and working on classic sports cars. Those keep me more than busy.