Is the PhD thesis needed for a faculty appointment?
One of the general prerequisites in this day and age for a faculty appointment is an earned (as opposed to honorary) PhD from a (typically accredited) degree-granting institution. 

Consequently, asking to see either a PhD thesis, a transcript, or the degree certificate is would be ways of ascertaining that you do, in fact, have a valid degree. This by no means implies that only your PhD matters in the hiring process; just that it's part of the process to ensure you're eligible. I wouldn't read too much into this beyond that.