It’s highly illogical to question why some students in IIT leave high-paying jobs and join graduate schools for Ph.D. This is because some people tend to do whatever makes them happy rather than following the sheep mentality. They don’t consider money as the only source of happiness. And they know that a high-paying job will rob them of mental peace due to a lot of responsibilities they might not even enjoy. So they choose a happier and simpler part which is pursuing a Ph.D.
Another major reason why people may pursue a Ph.D. rather than working at a top company is their strong inclination to words academics, and they may not be satisfied with a bachelor's degree and crave higher studies in the form of PhD. Basically, the reason behind such a decision is subjective and depends solely On the particular individual, and cannot be objectified.
The common reason why people make such a decision is that they have more interest in studies and doing a job would hinder that passion. Doing a Ph.D. gives you opportunities to travel and enjoy life generally. That being said, it's not necessary that a Ph.D. is easy for everyone. It strictly depends upon one’s preferences and capabilities.
Most students of IIT Bombay who leave their high paying jobs and join grad schools for Ph.D., do so for their love of research and innovation. Working on problems you discover and coming up with new approaches can be enthralling and rewarding.
Earning six figures is great, but earning one-third of that amount as a grad student doesn’t mean you will be poor. You will get fewer luxuries, but the amount of money is sufficient to make a comfortable living. Pursuing a Ph.D. will give you an extended college life, as well. Being in school can be quite fun.
After completing graduation, many students of IIT get jobs in top companies too with good packages but some of them leave these high paying jobs and join grad schools for PhD. Working in these companies and earning six figures can be great but earning less than half of it while studying isn't bad too. As after completing your PhD, you will get a job with a higher salary but still, a person who has already worked for 6 years in a company will earn more than you. So people don't opt for Ph.D. just for a higher salary, there are other reasons too.
Interest in Research
Student Life
Thus, students willing to study and research more about a particular topic or subject, they go for a higher degree. For these students learning about the subject has a bigger priority than high-paying jobs. It depends completely upon the individual and their interests which makes them either go for a PhD or a high paying job.`