The headline should actually say “S&P 500 index maintains existing rules for inclusion” They are not actively rejecting any of the three companies, any of them can join the S&P 500 once they meet the inclusion rules, but none of the three companies meet the criteria at the moment.

It’s not active rejection, they simply don’t meet the criteria to join the S&P 500 yet. The inclusion rules don’t completely prevent garbage stocks from being added, but it helps keep out the most egregious frauds, but even then an Enron will happen every so often.