Most owner-led businesses did not design this. Marketing arrived later, as a website and then an agency reporting on leads and reach. Sales was there from the start, reporting on closures. Each side's numbers make sense alone; what is missing is the plan that connects them, and until it exists that connection is you.
Why it persists. Each function is doing its own job well by its own measure. Joining the two means designing them as one system, which in a small business falls to the owner, who has neither the time nor a neutral partner for it. More marketing or another salesperson always feels more productive than connecting what already exists.
If it stays unresolved. The business keeps buying growth at the top of the funnel and losing it in the middle. Costs rise faster than revenue, capable people on both sides get blamed for a structural problem, and the owner stays the bottleneck for every commercial decision.