Amp FX Send/Return Chain

My Standard pedal setup is:

Comp - Distortion - Trem - Phasor - Delay - Reverb - AMP's PREAMP - AMPS's POWERAMP

What's the point of using the Amplifiers send/return inputs for FX?

They say you that modulation FX sound better AFTER applying any gain...but if I am not using the overdrive of my AMP is it worth it to go:

Comp - Distortion - Trem - Amp's PREAMP- Phas - Del - Rev (IN AMP FX) - AMP's POWERAMP


basically, who uses the AMP's effects chain input and why?

It's so you don't run your input through a bunch of pedals and lose signal quality or whatever.