Imagine our elected representatives trying to come up with laws, regulations, tax policies, public health issues (think big tabacco), arrests (there are currently many more alcohol related arrests than drug related arrests).
Not saying that this isn't something that shouldn't be considered, just pointing out that it isn't without cost.
One benefit of having many different jobs is that you meet a lot of awesome people in your field. And if you actually are good, then these ex-colleagues will probably invite you to new opportunities when they hop themselves.