Maybe just moving seats around. As someone stated IAH is going 2x about the exact time this stops. seems like the best guess.

People are paying a premium in the winter but summer people have alot more time and probably ARE willing to connect to save a penny. Ie i bet they get alot less people willing to pay a premium in the summer, so it goes. United is using data more than ever and can see exactly what makes money. People in the seats doesn't mean its making money if they are not willing to pay a significant premium to overfly so many United Hubs. Its about making money , not what has people in the seas

Also as a reference using great circle general routing. EWR-HNL is literally 1 mile shorter than EWR-ORD-HNL so you are literally overflying hubs. If they are not getting a significant premium people are willing to pay for a N/S they should cut the route. Also NYC/BOS-HNL has gotten quite crowded these days. There was a time when United was the only airline in Northeast-HNL now Delta and Hawaiian are all over it. They are probably not getting the premiums they used to get for the N/S in summer