I'd also like to know why. I've finished watching the first three series and I was very sorry to see Max go as for me he was the best character in the show. His replacement in series three was awful.
I liked them all, I don't know but I guess that Peter Woodthorpe might have wanted to leave to do other things, his CV didn't slow down after Morse and he was working solidly in TV and on Radio beforehand. I loved Max and gave a cheer in Endeavour when he was first (re-) introduced.
It has to be said that with the two actors playing Max and Morse in Endeavour, it was only 20 years to the start of "Inspector Morse" and neither aged well if they go from a to b.
Was watching The Last Enemy last week and my 18 year old couldn't believe that Inspector Morse was only 46 - looks 60 if he's a day.
I also liked Amanda Hillwood having fallen in love / lust with her in "A Very Peculiar Practice" - They filmed it at my Uni. and I saw them filming. Matt Frewer / Max Headroom is one lucky son of a gun!!!
And Laura, it goes without saying is an utter, utter babe. "I'm looking for a chief Inspector Mouse?".
Max had one type of scope and he probably left the show to pursue other projects. And Laura provides a different sort of scope and allows for other interesting story lines, especially the one where she is meeting an old collage buddy for supper and has the worst kind of surprise when she is called to a murder scene and it's her old college buddy who is the victim.