Does rushing work in a PhD happen by nature (of the degree) or is it applied (by supervisor)? A research paper may take several months to understand for a beginner, based on its complexity. Although a student is good with the required background in that broad domain, she has to understand several other research papers in backward chain, which takes a lot of time.
So, I feel that PhD is not a degree which has an inherent property of rushing.
If it is true, then why do most of the supervisors do rush their students instead of leaving them for sufficient amount of time? Is it a phenomenon in developing countries only or is it a global phenomenon?
Note: Rushing in the question refers to the phenomenon of asking student to perform a task (including publishing, comprehension) given insufficient amount of time, which may cause tension, panic or sense of urgency in students.
A research paper may take several months to understand for a beginner, based on its complexity. Although a student is good with the required background in that broad domain, she has to understand several other research papers in backward chain, which takes a lot of time.
So, I feel that PhD is not a degree which has an inherent property of rushness.

You have it backwards. The fact that reading, understanding, and producing research takes a lot of time is precisely why a PhD is often stressful. You have a finite amount of time to do a lot of something that's inherently time-consuming. That means you have to hurry / crunch on occasion, otherwise you aren't getting done what's required in the timeframe of your PhD.

why do most of the supervisors do rush their students instead of leaving them for sufficient amount of time?

I'm not sure if &quot;most supervisors&quot; do this, but if you feel you aren't getting enough time for your tasks it may boil down to one or multiple of the following:

You are going too deep (e.g., when reading previous research), and your supervisor is trying to nudge you to progress in your own work instead. Alternatively, if you are working on your own research, it may mean you are going too deep on one task and the supervisor thinks this has been done well enough and you should move on now.
Your supervisor has extrapolated that with your current speed of progress you will not finish your PhD in time (especially in countries with hard time limits this can threaten your PhD entirely).
Your supervisor is trying to establish a sense of urgency. Especially early on, a hard deadline five years from now can seem like nothing is even close to high-urgency, which for some people can translate into a lack of motivation to get stuff done right now. Having your supervisor ride your behind is a time-tested way to resolve this dilemma.
Your supervisor is unreasonable and is trying to squeeze too much out of you. Of course, what's &quot;too much&quot; depends on many factors, including legal requirements, standards of the institution, supervisor, and student.
[The worst case] Your supervisor values numbers over quality and is pushing you towards sloppy work.