What is the point of seperating analog ground and digital ground if they are going to meet at the end
The simple answer is that it keeps digital and analog ground currents separated. Digital ground current is typically "noisy". If the analog and digital ground are intermixed, noisy digital ground currents can induce noise into the analog parts of the circuit. 

But if the circuit is configured properly, the digital and analog parts of the circuit are kept independent except at one controlled point configured so that digital ground currents don't enter any parts of the analog circuit. This is often back at the bulk smoothing/filter capacitor at the output of the power supply.