Personally, I don't use schematic representations (wrongly maybe !!).
I think schematic representations can be more practical if you want to simulate a movement, although it's doable via a sketch (if you put all the necessary dimensions).
The explanation of SolidWorks, below, will enlighten you a little more... Or not:
As far as I can see, the only difference between a simple "skeleton" sketch and a schematic representation is the management of mobility, because the schematic representation manages the fact of making parts "move" between them (according to constraints defined at the sketch level), whereas a simple sketch will handle it little or very badly (once the pieces are created).
In short, for a "static" assembly => simple sketch, for a mobile assembly = > schematic representation.
Thanks @mdelbecq, indeed it is possible to create moving parts with schematic representation. If we wanted to do the same with sketches, we would have had to create a sketch for each piece.