There are plenty of people still hedgelaying. personally I know a few people who spend their winters out laying hedges - contracted to do so by other landowners. In fact, some ten or so years ago there were regenaration grants availably with Welsh Government under the tir cymen scheme (I think) with farmers being encouraged to cut down ailing/straggly hedges to the base to encourage new growth so that a few years later the hedges could be relaid, the grants included money to put up fences to replace/protect the hedges until they grew back the pigwire they used was not as good quality as normal as it wasn't meant to last forever, if I remember it had a greenish tint and people around here labelled the cheaper wire 'tir cymen wire'
Of course, every area has its own hedging style, our area has a method which is much easier to work and just lays the branches down and secures them with forked sticks made from the thinnings they discard, when the ditches were then cleaned, the soil dug out would be deposited on top of the hedge which slowly over the years would develop into a bank with the hedge growing through it. Hedgelayers in the Rhandirmwyn area were renowned for their neat, good looking hedges which also entailed weaving the new horizontals through vertical stakes making the hedges virtually indestructible and they were much in demand in the surrounding area
) and I can see they don't seem to be a thing in the UK ,I assume that's because you don't irrigate crops much?
