Because to be a chemist you need to graduate in chemistry.

What would be the point of asking theoretical questions?

There's just no way in hell people can remember even 10% of what they studied in college, book knowledge isn't really the goal, rather than teaching you how to learn and master the topics.

Because to actually have those types of conversations you have to have legitimate experience. To be a bit flippant, here's a relevant xkcd[0]. To be less so, "in groups" are pretty good at detecting others in their groups. I mean can you not talk to another <insert anything where you have domain expertise, including hobbies> and not figure out who's also a domain expert? It's because people "in-group" understand nuance of the subject matter.

[0] https://xkcd.com/451/

Doesn’t that comic more closely hew to the idea that some fields are complete bullshit?

That's one interpretation. But that interpretation is still dependent upon intra-group recognition. The joke relies on the intra-group recognition __being__ the act of bullshitting.