I think i can shed some light on the case, from perspective of what could be a type A, or some middle ground. (Since i recovered and started to be more if a B in traits)
Growing up in toxic and, honestly, disfunctional family (like i)... kinda takes the toll on you.
These "A" people often have trouble trusting people (for obvious reasons), so they do not really try to make new friendships or relationships.
Also will likely not try anything new, or will not do so with much effort, because, for them, success was either ignored or punished, and failure was punished hard.
I could continue, but this is not a venting reddit.
So just a word of advice for those who are not the type "A". Befriend those people and teach them to be more like you, because having to recover from having a childhood (sad that such sentence is real) is one of the worst things one can experience.