Electronics has been a hobby for as long as electronics has existed. It started with radio in the early 1900s, and has continued to this day. Audio was a big focus in the 50s and 60s, but hobbyists turned to micros, computer kits, and PCs in the 70s and 80s. That interest in micros continues to this day.
There have always been publications covering the hobby aspects of electronics, and today multiple websites serve this community. It’s hard to pin point the number of participants, but in general, the hobbyist population appears to be growing. Many working engineers are also hobbyists. Are you one?