I'm automatically thinking it's unglamorous, and marking a career plateau (perhaps decline).

I think to do serious maintenance work one would have spend lot of years in industry/company/project etc. If these people are just motivated by glamorous work, ever increasing career growth, they don't seem to me great maintainer material.

I apply this to me in narrow way to support a long running in-house enterprise product which I am kind of maintaining for many years. I just do not feel motivated by glamorous role and climbing on greasy corporate pole.