If it does seem weird, that indicates a fundamental misunderstanding: all potentials are relative!

You can choose any potential you want as your "0V" reference - the only issue is whether any other point is "more positive" or "more negative" relative to your chosen, arbitrary reference point.

In the Good Old Days of PNP Germanium transistors, it was customary to have the positive battery terminal as the "0V" reference or "ground", and Vcc would be negative with respect to that chosen reference.

Thus the schematics were drawn with the positive battery supply line at the bottom
Examples:
http://www.hilberink.nl/plaatjeshans/airchief.jpg
http://www.hilberink.nl/plaatjeshans/transch1.jpg