You're 100% right about knowing the limitations of your airplane.
The problem is that many airplanes (Saabs, for example) are performance limited at HXD because of the available runway for landing, and those performance limitations have a financial impact. Sure your Dash or my CJ or a Cirrus or a King Air don't have any problem, but there are lots of other aircraft that are severely restricted because, even if the runway isn't lengthened, they won't take down the trees from the approach end of 21. This is true especially when wet, where having an extra 300' available for landing could make the difference between getting in and airborne holding to burn fuel or a divert.
The fact that there's no glideslope on the LOC 21 is another limiting factor for HXD because it, well, limits the airport's usefulness to you when dealing with low ceilings and/or fog which often hang juuuuuuuuuust over the island off the coast. Sure SAV is 10-15 minutes away by air, but wouldn't MANY operators (maybe even Piedmont) stand to gain both operationally and economically from a precision approach and/or no displaced threshold on 21?