Because they want to exhaust the person engaging in a good faith discussion. It’s far more labor intensive to have to look for, find, verify for contextual correctness, quote and link said sources, then argue why one’s position is factually correct.
And all the other person has to do is cite some patently false bullshit in 5 seconds and disregard the argument.
Aka, “Why Don’t You Respond to Criticism?”
It all boils down to bad faith. They don’t care what argument you make, you’ll never sway them. They’re not interested in the debate with you as much as as they are just getting their bullshit out there for randos to read. Like you say, while you’re finding sources and making sure everyone agrees on terminology they’ve already said 3 more things that are completely wrong.
Ding ding ding. I actively refuse to do homework from randos on the internet.