it depends how you define accuracy, though most scales are useful regardless. if you step on your scale three times (an analog scale) and it reads just about the same all three times, it's repetitive use is accurate. step on that same scale in a week and it reads less, congratulations, you can almost be assured you lost weight.
analog scales have one advantage in that being spring loaded, the weight distribution on the scale is much less sensitive than electronic scales. those typically use four discrete strain gauges near the four corners and they depend a lot more on your weight being evenly spread out over the surface of the scale.