I do mum's windows as she's elderly and lives in a high rise. The windows are classed as fully reversible so they essentially turn all the way round for cleaning, well, most of the way round. however there's no way older people could easily do it, or those that don't have a head for heights.
What I've noticed is if I use good old warm water and washing up liquid, the windows don't stay clean for that long in real terms. However if I use window/glass cleaning spray and cloths they retain a degree of cleanliness much longer.
Conny's experience is quite similar to my own past experience of modern window cleaning. Except now they go around as a team, with a Transit fitted with a large water tank, a very long pipe and long brushes. They pull up in one place and the hose reaches around to several properties, but with the long pole, they cannot properly wash down the upper storey sills and it is no longer cheap.
Doing them myself, I am much more thorough. As said, I do have ladders, but the longer ones needed for the upstairs are far too heavy, so I tackle them from inside. The all but one, side hung windows, don't turn completely around, but there is just enough space at the hinge side to squeeze my arm through with the mop and squeegee. I can also reach the outside sill with a brush to clean that.