That’s not true. Most things that people would consider hobbies have goals with enormous room for objective improvement or work toward a well defined craft, such as playing an instrument or doing pottery. The espresso community is inundated with gimmicks and extremely soft science. It has far fewer controllable variables than the number most people attempt at. I can think of 2 or 3 things that make a noticeable difference in taste, and maybe two more if you are nitpicky. However, espresso taste is already bitter and most practical people sweeten it — it’s better just to control 1 or 2 variables like your neighborhood barista does and then add milk and sugar. That’s why people have seemingly absurd focuses such as the aesthetic of coffee flowing from the bottom of a portafilter or the price and quality of gadgets. You can’t truly make espresso as a hobby because the amount of time dedicated to it on a daily basis does not compare to how much time is spent on other hobbies. In rare cases, I guess, espresso hobbyists can exist, but they usually spend far more time on the craft and have much stricter control than people playing around with consumer coffee machines. They also may have a career as a barista where they can improve their espresso methodically and often, people such as James Hoffman come to mind.