Although personality traits might partially explain this, I think you're ignoring powerful systemic incentives too, especially in lab sciences.
First, tenured faculty in lab-science departments are often expected to cover most (~75%) of their own salary via grants. While tenure means you can't be outright fired for not doing this, there are still consequences. Some places will actually reduce your salary (so you have a job, but are now making $25k/year!); others won't do that, but your office can be moved to sub-basement 4 and your assigned classes will be held Monday 8-9am and Friday 4-6pm.
Tenure also only covers your own job. If you run a large lab, students, postdocs, and technicians depend on you for advice and funding. There is—or should be—a decent amount of pressure to be responsible for them, many of whom you've worked closely with for years. To do so, you need to write grants that fund their day-to-day work, revise their papers, and train them.
Finally, even if you don't care about your salary or your people, you probably do care about your own research program. These don't do well with lapses in funding. Preliminary data is essential for grant applications, but it's expensive and time-consuming to collect. Normally, some "falls out" of other, on-going projects: the project looking at how Xs become Ys sometimes detects Zs instead, so here you propose to look at the X->Z pathway. If your funding dries up, you won't have that data source. Without money, you can't get the preliminary data you need to...get money. Since the consequences of running out of money are dire and funding rates are terrible (~15% of grants get funded), the solution is to submit lots of things, which requires lots of work.
These factors explain a lot more, IMO, than personality/egoism. (And the age thing is about more than egoism. If you don't get a "real" job until 40, it's only natural to hang onto it for a while. And age is a terrible proxy for performance: some older profs do awesome work; some younger ones chase the trends du jour).
First, tenured faculty in lab-science departments are often expected to cover most (~75%) of their own salary via grants. While tenure means you can't be outright fired for not doing this, there are still consequences. Some places will actually reduce your salary (so you have a job, but are now making $25k/year!); others won't do that, but your office can be moved to sub-basement 4 and your assigned classes will be held Monday 8-9am and Friday 4-6pm.
Tenure also only covers your own job. If you run a large lab, students, postdocs, and technicians depend on you for advice and funding. There is—or should be—a decent amount of pressure to be responsible for them, many of whom you've worked closely with for years. To do so, you need to write grants that fund their day-to-day work, revise their papers, and train them.
Finally, even if you don't care about your salary or your people, you probably do care about your own research program. These don't do well with lapses in funding. Preliminary data is essential for grant applications, but it's expensive and time-consuming to collect. Normally, some "falls out" of other, on-going projects: the project looking at how Xs become Ys sometimes detects Zs instead, so here you propose to look at the X->Z pathway. If your funding dries up, you won't have that data source. Without money, you can't get the preliminary data you need to...get money. Since the consequences of running out of money are dire and funding rates are terrible (~15% of grants get funded), the solution is to submit lots of things, which requires lots of work.
These factors explain a lot more, IMO, than personality/egoism. (And the age thing is about more than egoism. If you don't get a "real" job until 40, it's only natural to hang onto it for a while. And age is a terrible proxy for performance: some older profs do awesome work; some younger ones chase the trends du jour).