Actually, bypass and electrolytic capacitors filter noise in different frequency ranges, high and low,
respectively.
Although the capacitive reactance formula, Xc = 1/(2pif*C), indicates that the impedance of a
cap should be even smaller at high-frequencies than at low-frequencies, for real-world electrolytics,
this is not the case [real-world always varies from the ideal]. See curve here,
The bypass cap works at those higher frequencies where the electrolytic cap impedance goes
back up.