Question

why You store less charge on series capacitors than you would on either one of them alone with the same voltage!

Answer 1

Capacitors i series have the same charge and the voltage will be distributed over them.

\[U ={ U_1 + U_2} = {Q \over C_1 }+{Q \over C_2} = Q \left( {1 \over C_1} + {1 \over C_2} \right) = {Q \over C}\]

Answer 2

for simplicity take 2 capacitors of same capacity c ,
when they are in series with voltage V then the resultant capacitance will be
C =c/ 2
it will store less charge as compared when both capacitors are connected with voltage individually