Why did KISS part ways with Ace Frehley and Peter Criss?

Answer 1

During the late 1970s, Criss's problems with substance abuse escalated, and he became increasingly frustrated with his role in the group. Criss left Kiss in May 1980 to begin a solo career. He released three albums over the next 15 years, none of which met with any success.
In 1995, Criss performed with Kiss during their appearance on MTV Unplugged. In April 1996, Kiss held a press conference to announce a reunion tour with all four original members. The 1996–97 Alive/Worldwide Tour was an enormous success, and the reunited Kiss released a studio album, 1998's Psycho Circus.
Criss remained a member of Kiss until 2001, when he left over a contract dispute. He rejoined the band in 2002, but departed again in March 2004 when Paul Stanley and Gene Simmons opted not to renew his contract.

Frehley found himself increasingly at odds with the musical direction of the band. After Peter Criss left Kiss in 1980, Frehley was often outvoted 2-1 in band decisions, as replacement drummer Eric Carr was not a partner in Kiss and had no vote. Frehley's participation in the recording of 1981's Music from "The Elder" was far more limited than with previous albums. This was, in large part, due to his unhappiness with the band's decision to create a concept album rather than a straightforward rock album.
Exacerbating the situation was Frehley's escalating erratic behavior and substance abuse. In April 1982, Frehley was involved in a serious automobile accident (although Anton Fig was the driver). In May, he led police on a 90-mph car chase on the Bronx River Parkway. This incident led to a $600 fine and a six-month suspension of his driver's license.[3] Although Frehley appeared on the covers for 1982's greatest hits album Killers and studio album Creatures of the Night, he had no involvement with either project. Frehley's last appearances with the band were the video for "I Love it Loud," a series of European promotional appearances in November 1982 and a band interview with MTV in early 1983 promoting their world tour.

Answer 2

Peter Criss left KISS in 1979 after the release of their album "Dynasty" in which he never played drums on all the songs on the album and drum chores were shared by drummer Anton Figg, later of Late Night With David Letterman fame. According to Gene Simmons, Peter could not balance his drumming and drug usage at the same time. After leaving Kiss, he started his own band which flopped and was in an altercation which included beating up his then wife.
I read on YaHoo! Answers not to long ago, a roadie that worked with KISS on recent tours, responded to certain question about Peter Criss. This guy said KISS had to hire another drummer for their last tour because old Peter can't play his chops any more like he did in the old days. This dude sounded authentic truthfull
Ace Frehley left the band two years later but I never heard what the reasons were. It was obviously on account of personal differences that could have been spurred on by Gene Simmon's and Paul Stanley's growing alliance inside the band.

Answer 3

Maybe Ace and Peter parted ways with KISS.

Answer 4

Probably money issues .