Why the actors who left the show, left?

I'm referring to:
Lee Norris (Stuart Minkus)
Lily Nicksay (the original Morgan)
Danny McNulty (Harley Keiner)
Blake Soper (Joey the Rat)
Alex Desert (Mr. Eli Williams)
Ethan Suplee (Frankie the Enforcer)
Anthony Tyler Quinn (Mr. Jonathan Turner)

Why the actors who left the show, left?

I'm referring to:
Lee Norris (Stuart Minkus)
Lily Nicksay (the original Morgan)
Danny McNulty (Harley Keiner)
Blake Soper (Joey the Rat)
Alex Desert (Mr. Eli Williams)
Ethan Suplee (Frankie the Enforcer)
Anthony Tyler Quinn (Mr. Jonathan Turner)

Lee Norris= left on his own decision for his own career aspirations; didn't want to be known only as a "geeky" kid.
Lily Nicksay= focus on school
Danny McNulty=role written off by writers/producers
Blake Soper= role written off by writers/producers
Ethan Suplee=role written off by writers/producers
Alex Desert= left to focus on his band
Anthony Tyler Quinn= written off because his role was jr. high teacher and the writers felt it more realistic to have new teachers in high school years.

Lee Norris= left on his own decision for his own career aspirations; didn't want to be known only as a "geeky" kid.[

Too bad his career went absolutely no where. Here we are in 2011, nearly 20 frickin' years since he was on the show, and he's STILL known as nothing but Minkus from his short 1 season run on BMW. Shame really.

Ethan Suplee=role written off by writers/producers

Now here's the one actor who I thought had left to pursue a career in film being that out of all the actors on the show, he's had the most post-BMW success with roles in movies like The Butterfly Effect, Mallrats, American History X, Cold Mountain, Unstoppable and so on. And of course I can't forget about his run on My Name is Earl.

Anthony Tyler Quinn= written off because his role was jr. high teacher and the writers felt it more realistic to have new teachers in high school years.

Yet they were content to have the kids Principal follow them from middle school all the way to college! Or turn Eric from a relatively intelligent older brother to a borderline ******** lunatic. LOL! Silly illogical writers.

Too bad his career went absolutely no where. Here we are in 2011, nearly 20 frickin' years since he was on the show, and he's STILL known as nothing but Minkus from his short 1 season run on BMW. Shame really.

I never watched the show, but someone on here was saying that Lee Norris is on One Tree Hill.