There is more flexibility on routes over the middle of a trip than near the departure or arrival constraint. Flight over large bodies of water tends to be away from the arrival or departure airport.
Going 100 miles out of your way for weather at a point that's 100 miles from the airport is a big diversion. Going 100 miles laterally out of your way at the midpoint of a 2500nm trip is about an 8 nm deviation (4nm out and 4nm back).
Also, I recall worse turbulence over land and smoother over the ocean. I’m assuming that’s just random luck and not a real thing?