Pollard trees are not common in North American landscapes. Interesting how often I see them in photos from EU. Not a value judgement, just a curious fact.
They keep our river banks and creek banks intact with their roots.
The fresh trimmed shoots are traditionally used to make baskets and other types of containers. Good firestarters too.
The hedges you see in the last pic are part of a unesco heritage called the Maasheggen (literally Maas river hedges, Maastricht is named after the river). Mostly hawthorn and blackthorn. They feed the birds that eat bugs, act as wind breakers, and they're cheaper than fenceposts. Every year people saw through 40%-60% of the trunk and lay them down horizontally to produce an inpenetrable hedge. But the tradition is slowly dying, it's hard work with no pay and it serves very little purpose lately since it's easier and faster to do regular fencing with barbed wire. The hedges are trimmed with machines since a decade or so, so the quality of the hedges is degrading as well.