A lot of the older places on this shore started as a cottage and got added onto: a porch enclosed, a sunroom put on the back, a garage finished, a room built over it. Almost none of those additions got their own ductwork, because running duct into a space that was built after the ducts were is expensive and often impossible.
So the room ends up on a window unit, a space heater, or nothing, and it becomes the room nobody uses for four months of the year.
A mini-split fixes that without any ductwork at all. An outdoor unit, a small line set through the wall, and a head inside the room. It heats as well as it cools, which matters more than people expect: a three-season room becomes a room you can sit in in February.
The oldest cottages take this further. Some of the pre-1970 stock has no ducts anywhere, just window units and baseboard, and for those a multi-head system is often a better answer than retrofitting ductwork into a house that was never designed for it.