I imagine it’s because it’s the simplest, most common type of ball that you commonly see described as such. Like, baseballs and basketballs and soccer balls and beach balls exist, but out of context they’re typically called that rather than just “a ball”. So, a simple round ball. Giving it a pattern requires some extra thought, and of the solid colors red seems like the most common (think dodgeballs).
While anything that gets people off Twitter is good, I’m sorely unimpressed by those artists who “had to” to patronize the racist transphobic neo-Nazi hellhole “because my audience is there”… until Musk’s policies happened to offend their own personal interests, by requiring training for their AI. Countless models trained on all public images already exist, jumping ship won’t prevent their work from being scraped elsewhere, and frankly, any one image or even portfolio will contribute virtually nothing to the result, so quitting in protest is largely symbolic. But so many peoples drew the line at that, and not at Musk making “cis” a slur, or protecting child pornographers, or boosting white supremacist supremacy theories. It’s really disappointing to see.