This is the difference between an amateur and a professional. An amateur starts performing for themselves, what they are interested in, what they like, what they've seen other's do and think "I wanna do that," and all based on their personal tastes and preferences. As Danny said, this is fine for amateurs, hobbyists and tinkerers. However professionals must look at it differently. It is no longer about you, it is about so many others - the booker or person booking you, perhaps an agent, producer or promoter, the venue or event, the performance market, perhaps event sponsors, and yes, the performance audience.

Same for creating a show - an amateur, hobbyist, or tinkerer creates a show based on themselves and their wants, likes and interests, a professional creates their show for the market and the other factors mentioned above.

I remember David Thiel telling a story of when he was making the transition from magic to mentalism that he could no longer perform his favorite signature trick from his magic show as it didn't fit or wasn't congruent with his new mentalism show and markets. As much as he didn't want to he had to give it up.

The whole thing is different from the way to think (mindset) and approach your show and the business behind it, to your persona, material, performance dynamics, and literally so much more.

So if this entails performing something you don't care for... But to do it for no specific reason or purpose...why?

The sad or great thing (Depending on your point of view) is that very hard (for some) fact that you have to learn is that you are there to entertain the audience, not just for you to enjoy yourself.
Entertain an audience and you will get work, don't and you won't!

So, get your kicks and pleasure from doing just that and not in the particular routine you are doing.

Many famous singers have experienced this as they love one song that they do but the audience just go mad for that one hit that you hate that went to number one 10 years ago. Sinatra didn't particularly like "My Way" but he always did it as he was there to entertain the audience, not himself.

I have seen way too many amateur magicians who think that they are great and love being the center of attention performing the lastest trick that they think is great. They bomb!
Conversely, I have also seen many who get that they are there to entertain the audience and after doing just that, they get their enjoyment from the audience telling them how wonderful THE AUDIENCE thinks they are. They get return bookings.

Not a bad illustration of the difference in professionals and amateurs.

I liked performance better when the marks bought the tickets and not the performers.