Behind our townhouse there's a strip of lawn at the foot of a sloping bank up to a strip of the woods which remain from the original landscape before the townhouse cluster was developed. Originally when I bought the townhouse from the developer the bank was planted to grass. When the maintenance company's crew mowed the lawn it also mowed the grass on the bank. For a few years.
Unfortunately the bank was good Virginia red clay, so the grass never thrived. It was invaded by weeds, which soon the mowing crew decided not to cut. Over the years some woody brush has filled in behind the weeds, which have advanced down the bank and into the strip of lawn. Just the other day I noticed how narrow the strip of lawn had gotten, as each year the crew abandoned more land to the weeds.
The situation reminds me of the borders of our fields, back on the farm I grew up on. Something similar happened there. First you have a fence, and a few weeds grow up around it. The fence posts prevent you from mowing under the fence, so you mow within a foot or two of it. But areas which aren't mowed become a niche for brush to grow up, which shades the adjacent area, where the weeds invade next.
When mowing hay, you don't really want to cut brush which might get baled, or which might clog the cutter bar of the mowing machine. So each year you mow just a tad further away from the original fence, and so the brush becomes a hedgerow, and the hedgerow grows and grows.
Which is sort of like my sideburns. Particularly since covid, I go a long time between haircuts. When I shave each morning, somehow my sideburns become a little longer, meaning when I do get a haircut the barber needs to shave them back to their original place.
Bottom line: I think hedgerows and sideburns become good metaphors for what happens on the margins of states, the Roman empire, and organizations. Often the returns from maintaining them don't really justify the investment needed to sustain the difficult maintenance.