It's a plot to sell snack boxes. Nothing more, nothing less.
I expect minimal complaints honestly because people are so used to paying for everything at this point.
People that still fly UA t-pac are still flying UA for a reason (i.e. company policy, lack of trust in Asian airlines' pilot training standards, close to 1MM, concerns about English, GPU lottery, etc.) and they aren't going to switch to an Asian carrier just because they have to pay $7.99 for a mid-flight snack box.