The Ph.D. program, in our times at least, is pitched as a quid pro quo: you produce some original research, something worthwhile and of substance, to add to the sum of human knowledge, and in exchange they gain access to an academic career.
The problem is that there are a lot of people paying the quid, and barely anyone getting the quo. Unless you are a student of independent wealth, you are not producing this research out of the goodness of your heart with no greater, more important objective. To the vast, vast majority of people doing their Ph.D's, a Ph.D. is a career maneuver.