Because it's not possible to answer those questions without knowledge of how that plugin works, and it quickly becomes less about WordPress knowledge, and more how the plugins API works. We aren't a dev support route for 3rd party products and services, we're a WordPress developer stack focusing on WP itself and the official WP projects.
The result is that we get lots of questions that don't get answered or can't be answered, leading to an unhealthy stack.
A good rule of thumb is can the question be answered using general WP knowledge? Or does it require you to go to the plugins docs and read up on how their filters work?
Also from a cynical side, are they just dumping all their support requests who won't pay here? WooCommerce were notorious for this, though it was well meaning individual staff rather than a company policy. Some plugin authors put WPSE straight in their sites support menu. Note that doing this is against stack exchange terms and services.