I think I'm in the minority here. There are
plenty of subjects I would not read tarot on. In fact, the list of things I read tarot for is very short. I read tarot to see into my own mind. Its like a check in with my subconscious. I read tarot to learn more about the present rather than the past or the future. I also read tarot to inspire my creativity.
I don't read the cards about other people (friends, family, or anyone else), except when my friends expressly ask me to look into their own lives to offer guidance. I try to keep the readings for them towards exploring the present rather than learning about the past of the future. I don't read tarot for divination of the future. I used to, but as I got farther into reading the cards, this use seems to have fallen away.
I would also never read the cards about my health. Mood yes, health no. I also don't do yes/no questions.
I know other people do all of these things and do them well and successfully, and I used to do pretty much all of them as well. But as I learned more about tarot and how tarot can enrich my own life I stopped doing pretty much everything except using it as an exploratory tool for learning about my own mind and my own creativity. Using the cards for just those purposes keeps me busy enough. I may end up branching out again in the future, but right now I'm happy in my little corner of tarotland.