One natural answer is that they comprise continua, three-dimensional in the case of space, one-dimensional in the case of time; that is to say that they consist of continuous manifolds, positions in which can be occupied by substances and events respectively, and which have an existence in their own right.
It is in virtue of the occupancy of such positions that events and processes are to be seen as taking place after each other and substances are to be seen in certain spatial relations.
Or do space and time have properties of their own independent of the objects and events that they contain?
Did Einstein show, through his theory of relativity, that since space and time can change in shape and duration that space and time are more complex than just sustained perceptual constants?
