Why do small time actors wanted to become the lead and rise to the top in their career, if they claimed they never wanted fame?

This is just an out of curiosity question. I've watched some celebrity interviews online and at other places and there is this one thing that most, if not all these actors tend to say, "I never wanted to be famous. If actors don't get into acting for the fame. They do acting because they love it so much, then why do they complain about their lack of career progression, has toiled for many years in the entertainment industry and still have yet to achieve success! Although they had filmed in several tv series and films, but most of the roles they received were mainly minor roles and had never been given the opportunity to play heavier roles. If they really had never intended to pursue fame and fortune, then why are they so eager to gain recognition, make a name for themselves in the acting industry, rise to the top and achieve 1st lead status?