If you switch jobs, you're bringing your (outside) experience and ideas to your new employer, and they're paying a premium for that. You don't have outside exp

If you switch jobs, you're bringing your (outside) experience and ideas to your new employer, and they're paying a premium for that. You don't have outside experience to offer your current employer, so they're not paying for it. It's not (just) that the current employer is being stingy, an employee is actually more valuable to the new employer than they are to the current employer in some circumstances.