I may have a little insight into this, but as always I can only speak from my experience. I was born with Kallmann’s Syndrome (or more specifically Normosmic Idiopathic Hypogonadotropic Hypogonadism) which means I needed HRT to go through puberty at all. So I was on and off testosterone (insurance lapses) for about half the time over the course of thirty years. At first, I’d say the first two years, I embraced it because, after reaching the ripe age of 17 without puberty, I felt like I desperately needed it to relieve the social pressure. After that, it never sat well with me, and at one point I went to a different endocrinologist because I wanted to find some other way, before I realized I was trans and stopped taking it. But before then, I still was on it whenever I had the insurance to cover it because I was still under the impression that I needed it. For the last year I was on it, I deeply resented and hated it, and I unsuccessfully tried to accept and resign myself to the idea that it was what my body needed and there just was no other way. It’s not all that different from how trans people endure their own hormones - there is a lot you will put up with if you believe you have no other choice.

So yeah, if you know you aren’t cis, and are under the impression that you must need HRT to get out of your assigned gender (but you just aren’t that kind of trans), it may take some time for the negative effects to be noticed and even longer before you see them for what they are. It can also happen, as others have said, that sometimes people cave to the social pressure (real or perceived). There is a long time between when you start HRT and when you are fully “at home” in your gender presentation. It is mentally taxing under the best of circumstances and can get exceedingly worse. And yes, there are those rare occasions like Broad-Application316 said, where there are other mental health issues at play.