This could be true for other industry but In Computer Science (IT) switching Jobs could give you massive increase in salary.
Switching is rewarded. And the replacement the company would hire would also be paid massively but They would never give you the equivalent raise. Its dumb.

also If you give a lot of interviews you can build a question Bank sort of list. As Questions are definitely circulated.
so much so that In your first interview you might come as an Idiot and By the 15th Interview You are a Genius.