In sufficiently small companies yes it makes sense for everyone. In larger and more regimented companies doing the Greenfield project can (and often does) lead to promotions and higher earnings.
Teamwork is fine, but when salaries and promotions are individually negotiated you have to look after number one.
I have the highest rank and salary on my team. I am more than happy to send high visibility work to my aspiring team mates. What goes around comes around, if not in the form of immediate salary then in the form of connections and references down the road (which is a much bigger driver of salary and rank anyway).
Playing a zero-sum game at work at the expense of your colleagues is penny wise, pound foolish, even if you truly do only care about yourself.
The level of politics, promotion, promotion packets, leveling is a whole different level. That is not to start on PIP, hire to fire, etc...
You need to know the game if you're going to play it.