Why do people become docs that specialize in psych if they can't treat relatively common psych disorders?

I was just thinking on my walk about when maybe 10 years ago I started seeing this doctor who after a couple appointment said she refused to see me anymore because she didn't know how to treat bipolar disorder.

The very first time I sought treatment I was a teen, and I talked to the therapist for a bit and she said "I can't help you; you need to go to the hospital." (She didn't say anything correct about the hospitalization process. She said to go down to the hospital and ask for admission when they only do transfers from the ER. Also my mom was scared shytless I'd go and never come out because no one explained it'd be like a week.)

Little different but when my ED got really bad at the end of last year I had a psych involuntary admission where the unit wanted to send me to a specific eating disorder treatment. Two PHPs turned me down because I was too sick I guess, and then I had intake for inpatient and I wasn't sick enough, and of course my insurance doesn't cover residential...not like I didn't end up in the ER several times over the next few months for stuff like throwing up blood and having really low potassium...

I like my current pdoc. She's not afraid of anything!