Combo of factors:
1. It takes time for pricing and inventory algorithms to catch up with the drastic shifts in capacity and schedule. Much of the work will have to be manually/semi-automated.
2. In the near term, UA is also likely trying to (gently) discourage travel to leisure heavy markets in part to keep the peace with labor. The AFA, in particular, has been very vocal about its proposal for UA airlines to stop serving leisure markets altogether for the time being given the minimal upside relative to the health risks to crews.