Why do students go for a PhD even when chances of getting academic jobs on its completion are slim? This is in reference to my question: How to do a PhD to equip myself for a job as assistant professor.

I was told in the answer of the above linked question that chances of landing a job as an assistant professor in Mathematics are quite slim. Very few people will actually get a permanent position in academia.

An article of 2014 shows only 0.5-3% of PhD graduates will actually get a job as an Assistant Professor.

But I have two questions:


  
  Why do so many people still apply for a PhD in some reputed institutes in India even knowing the harsh reality? I found there are 1500 applications for four PhD scholarship positions. 
  
  
  One answer says that people move to industry, but I still don’t understand how after doing a PhD in suppose differential geometry or algebraic geometry one can do a job in industry if he/she gets no position as an assistant professor.
  Will one be satisfied to do some managerial work in some Consultancy firm after doing a PhD in Mathematics?
  
  Are people jobless after a PhD?
  Completion of a PhD requires so much effort. So why is there no value after doing it?
  


NOTE:

In the most up-voted answer below it has been said that many who enroll for  a PhD don't even wish to pursue an academic career.

I have been asking my seniors who are currently pursuing a PhD or are in the verge of completing their degree or who have completed it.
They said that they all want to be Professors in some Universities and want to be involved in research because that is the dream job for them.

I am obviously talking about PhD in Mathematics
The issue is that the frame of your question is wrong. You’re assuming that the purpose of a PhD is to get an academic job, when that is not the case: Many people who get PhD’s have no desire for an academic job, even from the time they apply!

The number of academic positions is indeed insufficient to absorb all the PhD’s. But there are lots of other “landing spots”:


Industrial research and development
Start-ups
Non-university government research institutes (like the US NIH or DOE lab system, or the Max-Planck-Instituts in Germany)
Finance and consulting
Administrative and Supervisory positions in other disciplines.


Overall, PhD’s have a lower unemployment rate than non-PhD’s. It’s all a question of where they want to go.

As for doing a PhD, the basic skill it teaches you—the one that makes you valuable to lots of people—is the ability to learn new fields quickly and become an expert in those fields. You don’t always need specialized knowledge in your PhD topic to get into an area.

But ultimately the reason for doing a PhD is the love of research and discovery. People pursue research careers because that’s what they want to do.