If you overnight sail along the coast then I think it becomes more important, likewise if you sail out of season. There have been a couple of instances in the last few years when a yacht has suddenly capsized or been severely holed and sunk at night due to striking a submerged / invisible object - one incident in the Thames and one to the south of the Isle of Wight as I recall. The Thames incident prompted me to go and buy one. If all you do is sail in crowded waters where rescue is close by then the need diminshes, likewise if you are prepared to tow a fully inflated dinghy