It's unfortunately true that many companies are much more willing to offer money to lure new employees, than they are to incentivize existing employees to stay. Once you're working for them, they figure they don't have to woo you anymore.

So definitely jumping around a lot is a way to increase your salary in a lot of fields today.

The public sector is one of the few places that still functions the old way. You will never get the same pay that you do in the private sector - especially if you're in a highly skilled field - but everything is set up to retain people. There tends to be a more-regular progression in salary, at least to an upper limit. And the pensions are set up to improve as you accumulate service credits, and will often include bumps at certain milestones.