Why should you go to grad school? Because you want to do grad school.
If you are viewing grad school as something you have to grind through in order to get the faculty job you covet, don't go. Your chances of getting that faculty job are too low.
If you want the faculty job, you have to go to grad school. But you should believe that when you come out the other side, you will find grad school to have been a worthwhile experience even if you don't get the faculty job, and end up doing something (e.g. teaching high school, working in industry) that you might have been able to do without the PhD.
If you want to be a doctor, go to med school. Grind through it. You may not get a top job posting, but you can be pretty sure to be a doctor somewhere.
Even though grad school at least in Physics is still entirely designed to replace the faculty-- to make people into researchers in Physics-- the same very much does not apply. We produce way too many Physics PhDs for all of the faculty jobs and government research lab jobs that are out there. You have to want to go to grad school itself to rationally go to grad school.
Read the post I link to above. It's good.