Frankfriend -- Different firms still pay different "bonuses," but you're correct that it's pretty silly to call it a "bonus" when pretty much everyone does it and it's not really a "bonus" in the "usual" meaning of the word at all.
I'm told there might be some tax advantages to compensating your employees with different "types" of funds, though (salary, bonuses, medical insurance, etc.), and this might be one reason companies do it rather than just bumping up salaries instead.
If your goal is strictly to maximize your income, assuming you're talented in your field (but just want to work as a tech/engineer and don't plan to move into management), you definitely do better finding yourself a new job every 3-5 or so than staying at the same place *on average*. I would advise anyone who's single and just getting out of college to specifically plan on finding a new job every, say, 4-5 years for a decade or so prior to "settling down" at a company they really like -- you get a lot more experience, see a lot more interesting things, and in general are more valuable.
Somewhere in there you should put away enough money for 3-12 months of living and take a world-wide vacation as well -- while you may very well have another chance to do so after retirement, physically there are a lot of things you can do at 25 or 30 that you can't (or at least shouldn't) be doing at 65.