There hasn't been any actual reason as to why it is possible for some people to respond to ASMR while others don't. The tingling sensation that people experience as a result of ASMR can only be imagined by those who have experienced it before. If you haven't experienced it before, you can only be guessing as to how it would feel if you were to experience it.
One of the two ways through which you can experience ASMR is by thinking or meditating about a particular incident that happened when you were still young. You might also experience ASMR by thinking about a sound that you have heard before. Another way through which you can experience ASMR is when you are watching videos or someone who is performing a simple task and thereby making a sound that is very quiet, either through their movement or other methods. The tingling sensation from ASMR is usually a positive one.