UM service is important to separated families who almost by definition are financially constrained.
As an SLF in Canada, I have commonly seen UMs and they seem to be conscientiously looked after.
One of my most delightful flights was YHM-YYC on West Jet, an economy carrier, with 3 sisters in the row behind me on the way to their grandparents who took turns talking my ears off and showing off their various toys, fuzzy animals and coloring books.
And yes, the cabin crew kept an appropriate eye out at all times.