I may not understand the word fun the way you do here. Hiking is fun to me. Getting closer to the nature for a couple of days, resting from the city noise breathing fresh air etc. but when you go up high in the mountain say there's no more fun. You have to be well prepared with all the equipment and techniques and it's still dangerous if you go all the way to the top with people dying every now and then. There is some valuable experience that you get from that and there's emotions and plenty of that too but I wouldn't call this fun at all. Then after you become more proficient some of these routes are no longer dangerous to you and they become more fun and may become even boring. That's what I think happens with me and the music. Playing music is very rewarding but after a lot of hours it just becomes less challenging and more fun to do. this goes for both technique and feeling, cause as you play more you also find new ways to express yourself.
I define Fun is anything that can be an enjoyable experience.
The climber analogy works cept when it doesn't work. I used to rock climb and backpack, and still backcountry ski from time to time. The comparison is limited. Mountain sports is about pushing your own limits, the challenge is the fun itself along other rewards (like adrenlaine rushes). Enduring harsh conditions is never fun, but for whatever reason you always look back on it with fondness and the reward is knowing that you survived through difficult times. It brings a different kind of rush. Climbers do easy routes because they want to just to mellow out and get outside and reconnect with nature or just have a good time. You can't compare that with the type of stuff people do cilmbing Annapurna or K2. They're different worlds. And one persons molehill is another person's Everest - it all depends on who you are. The former is about enjoyment, the latter is about suffering through a personal trial.
Practicing your scales is only a arduous chore because you let it. If your practice is devoid of creativity, it'll become dreary quickly. It seems to me many people aren't very creative about their practice habits and finding out new ways to approach things that works better for them.
Example:
The difference with music (at least with playing jazz), is that basic material can be recombined or repurposed with something else to make it challenging again.
You are only limited by what you allow yourself and what your creativity can come up with.
Finally, Hal Galper's video on practicing should be required viewing.
