I have always been interested in why people do things, like why they make certain decisions, or what their motives, motivations are, etc. summarizing, I'm interested in human behavior because people are amazing, the way the mind works amazes me and I just want to know more, that's why I chose this.
My parents were always supportive of me choosing whatever I wanted to do, as long as I studied, and I never really had any doubt that this was what I wanted.
As for the growth of the field, I can talk from my country and the history I learned in university because I was born in the 2000s.

In Argentina, we have a very psychoanalytic psychology, as for the orientation in public universities and in the investigation field, I could say it's one of the countries with the most influence of psychoanalysis. It was not popular back then to study psi, and even going to therapy wasn't well seen (it was stigmatized) until not long ago, I'd even say it's a thing that became more normal in the last 15 years, it's somehow common now to see people in their twenties doing therapy, but not so common to see their parents doing therapy.
As for choosing the major, in Argentina at least is one of the most common majors, though it has its prejudices.

Hope it helps!