There are actually a number of cases where each method is applicable.
Continuous motion is tied to minimum possible speed (although this can be faked using speed averaging techniques), and therefore largely unusable for multi-day timelapses (say, one shot every hour for several days/weeks/months).
Additionally, there are a number of "artistic" effects that can be produced using either. For example, when shooting 30s exposures to eliminate moving objects, but still having static objects sharp, S-M-S excels. (Whether or not it seems "too sharp" is often a subject of debate, rather than land on one or the other side, it's a no-brainer to do both.)
Additionally, when working with really long lenses and macro work, any vibration, including that of a running motor can blow focus. For critical focus work with big heavy lenses, S-M-S can be quite useful.
A number of people use S-M-S for star work, as "tracking stars" also blows your foreground subjects - blurring and smearing them. It's ok for stars to trail slightly, as the mind understands them as moving objects in the sky, but if the tree in the foreground is a blur, it can kill a shot. "Tracking stars" works well when only stars are in the shot, with real foreground items that draw and focus attention, you want some flexibility in how you create it.
An extreme is to move during the shots more than between the shots. I describe the benefits and drawbacks of each method in a very short article here: Loading...
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