Type is about preferences, not strengths. You can have a preference but never have had the chance to develop it. For example, traditionally in this country women who preferred Thinking were socialized to step into the shoes of others and see how they feel (the Extraverted Feeling function) to make decisions, not to go with the logical course of action. If Intuitive children are told to stick to the facts, they may not learn to trust their hunches and thus effectively use Intuition.
When the preferences are allowed to develop (and the role of parents and teachers is to create an environment where that can happen...sigh...) then we see patterns in interests among people who share preferences. But to quote Isabel Myers, all ISTPs are like every ISTP are like no other ISTPs. You can pick up any interest because of a big brother, a favorite teacher, a great TV show, etc. Similarly, a natural interest can be stifled--NTs for example may learn to hate math if it's taught through a "memorize the procedures" text like Saxon math. I'm an NF and love math because it was taught well and I loved the patterns. On the other hand, I'm happy coaching math teachers, wouldn't want to be a U math professor.
And...each function can manifest in different interests. NTs might like the logic of philosophical argument rather than math. ISTPs might like the practical problem solving of parole officer work (I know two) rather than mechanical endeavors. INFPs might prefer the creative work of psychiatry or architecture to poetry. Etc.
Similarly, there are few ST philosophers (may enjoy a few classes, but who can get a job if that's their major, they say) and few INFP heavy equipment operators (you can't start daydreaming...)