Sounds like United is working on building that functionality into an AI-based chat flow, which might be effective for the average to infrequent traveler not familiar with the app's (or the web's) deeper functionality, which even though they seem pretty straightforward for us, are more power user-oriented.

Perhaps in the near future, if your flight delays, rather than a text message that is more of a one-way notification, directing users to the app, it can prompt a traveler to interact on the spot and proactively offer alternative airports. I can envision something like this, in real time without waiting like the current chat function that is run by a real person for higher level tasks:

"Sorry Mr. EWR764, your flight to EWR is delayed again. Would you like to see your rebooking options?"
"Yes"
"It looks like there are no other flight to EWR available today. There may be flights available at airports close by. Would you like me to check nearby airports?"
"Yes"
"Good news. There is a flight to New York-LaGuardia (LGA) available at 3:00 pm. That is 30 miles away from Newark (EWR). Would you like that instead?"
"Yes"
"You are confirmed on flight 9999 to New York-LaGuardia. Your new seat is 3B. Boarding begins at 2:25 pm from gate C9."

Alternatively, I might be more inclined to use the chat function if I knew it could recognize a prompt from a user ike this, if LAX options weren't favorable: "Can you check flights to ONT or SNA, but not BUR?"

If the chat tech was smart enough to parse that and get me what I'm looking for, that might be useful even for more experienced flyers, and definitely valuable for those who travel less often and can be at the mercy of a customer service line snaking down Concourse B in DEN, or a long wait time on a call to reservations.