My understanding is it sort of relates to a simulated acoustical physical space the music is intended to seem as if it is reverberating throughout
Is it correlated with the intimacy or closeness of the music, what else does it evoke? What is its relationship with artificiality and nature respectively?
What is its evolutionary purpose in terms of why we can parse and interpret it?
Reverb can be used for lots of purposes. As you say, it simulates reverberations a physical space.
Short, natural-sounding reverb can be used to blend tracks together. If two instruments need to sound like they were recorded in the same room, do it virtually.
As others have written, longer, natural reverbs can create a perception of size. You can make a vocalist sound like sang in a concert hall or a church or a bar.
Sometimes reverb may be used to impart tone, evoke a vintage. A spring reverb has different cultural associations than a Lexicon. Some reverbs’ modal resonances highlight certain frequencies.
Long reverbs can be used to increase sustain of an instrument. Every ambient guitarist in the world is familiar with this.
What reverb means in a piece is for the artist and listener to interpret.