Twitter language has started seeming normal casual to us, rather than us using normal casual language in Twitter.
Even if 95% of the spam gets actively reported and dealt with, that still leaves a ton of nonsense on the platform, getting fed into the LLM. And spam has only gotten worse over the years, as the barrier to entry has lowered and lowered.
You know people lie, right? Especially when the lie casts them in a better light and/or makes them more money.