Maybe it's because in Spanish we often use el rastro ‘trail (of an animal), footprints’ or la pista ‘track’ instead of using plural las huellas. Buscamos al venado siguiendo el rastro que dejó en la arena ("We looked for the deer following the footprints it left on the sand"). Le seguí la pista al venado por varias horas ("I kept track of the deer for some hours"). Using plural las huellas is fine though, but I'm saying it often sounds just as idiomatic to say el rastro or la pista instead.
huella can also mean "fingerprint" by the way.
This is how I also felt regarding English "wag" (as in look at the dog, it's wagging its tail). Similarly for some other Germanic verbs like wriggle, wring [a rag] and tug.