A feed makes a name familiar, and familiarity takes longer than a quarter
Social is slow demand creation. The product is recognition, and it will not fill next week's schedule.
Somebody in pain books with whoever appears first and answers the phone. Search and a map listing win that appointment, and nothing posted on a Tuesday competes for it.
A feed does something slower and worth more later. It makes the practice a known quantity to people who are not looking yet, so the name is already familiar the day the need arrives or a neighbor asks.
Anyone promising a full schedule out of a posting calendar is selling something. If chairs are empty now, buy search, and let the slow channel do the slow job alongside it.
Say the timeframe out loud to whoever approves the spend. A couple of quarters is the honest unit here, and accounts get abandoned around month three, right before the point where they start to pay.