Sounds like at that point (having quit Marvel) he didn't care as much (from wiki):
Moving over to a staff position at Marvel, Cockrum and Len Wein under the direction of editor Roy Thomas created the new X-Men, co-creating such characters as Storm, Nightcrawler, and Colossus. Storm and Nightcrawler were directly based on characters which Cockrum had intended to introduce into the Legion of Super-Heroes storyline had he remained on the title.[13] These characters made their debut in Giant-Size X-Men #1 ([July] 1975),[14] and then in a relaunched Uncanny X-Men(beginning with issue #94).
Journalist Tom Spurgeon wrote,
Cockrum stayed with the title until 1977 (as main penciller on issues #94–105 and 107), when he was succeeded by penciller John Byrne with issue #108.[15] (Issue #110, which Cockrum co-pencilled with Tony DeZuniga, was an inventory issue.[16]) The final issue of his run introduced the Starjammers, a spacefaring superhero team he had originally intended to debut in their own series.[8]
He and Paty Cockrum were married on April 28, 1978.[17] Cockrum quit his staff job at Marvel in 1979 and his angry resignation letter was printed in Iron Man #127 (October 1979)[18] but he continued to work for Marvel as a freelancer. Cockrum was Marvel's primary cover artist during this period,[13] and also penciled and/or inked a number of other titles for DC during this time. Although not a regular artist on the series, he re-designed the costume for Ms. Marvel.[19] When John Byrne left the X-Men in 1981, Cockrum returned to the title with issue #145 but left again with issue #164 (Dec. 1982) to work on The Futurians.[2]