I haven't ran aground in 27 years, the last time I did I had a depth sounder. Since then I have been using a lead line although I really don't use it that often. Sure there are forward facing sonars but I doubt many of us have those. So with all the excellent charts and charting devices we have these days is there really any reason to cut another hole in your hull? It seems like a depth sounder is really only good for telling you what you just hit but my guess is by that point you don't need an electrical device to inform you that you are hard aground or sinking.