TSS and Peacemaker are tied to the DCEU. Jason Momoa and Ezra Miller even show up as their DCEU characters at one point. If the goal is to do a hard reboot to distance themselves from what came before, that stuff has to go too.
Besides, TSS flopped, and the audience response to it wasn’t really that great. The DCEU in general had failed to leave an impression during Walter Hamada’s run.