Why? That has literally nothing to do with the issue at hand, a Ward on Probation abusing her position. How and why they volunteer for Endbringer fights has absolutely nothing to do with the issue, and the people in power have no desire to bring it up, because they need the warm bodies for Endbringer fights.
Seriously, this is a local scandal. No one even died. I mean, fuck, Police officers get away with shooting unarmed men all the fucking time and people don't demand the related branch of the Police stand down until the matter is investigated. Well, sometimes they do, but it never actually happens. Sophia's going to be in trouble, Piggot may be sacked or forced to resign, and there will be some reforms of the way the Wards handle probationary members to prevent similar cases in the future. There will probably be some form of damages/reparations paid to Taylor, some anti-bullying programs implemented, but they aren't going to cripple their Endbringer response just because.
Also, Contessa. She doesn't want Endbringer response crippled, so it won't happen.