Role of Pipe Length in Poiseuille's Law

I can't figure out why the length the a pipe (L) increases the change in driving pressure with respect to this law:

Delta P = (8*mu*L*Q)/(pi*(r^4))

I would think that delta P wouldn't change because the fluid is incompressible.

Does anyone have a conceptual explanation for the simple fact I can't seem to find?

Thanks in advance.