You are also right in that the more deliberate way to get an increased salary or position is to change jobs. Yes, it happens internally as well, but it's harder to achieve. Also, going through multiple jobs is better for both experience but also in seeing what the industry actually looks like. When you work at the same company for many years, especially if that's pretty much the only job you've had, then you have just one data point, which is to say, you really don't know much.
The job market isn't booming, though it does seem to be picking up.