What is the underlying rationale of this common sense?
Common sense could work in both ways, common sense could tell you that by joining an existing repo you could reach a larger audience quicker and easier but at a cost to individual reputation. Whereas on the flipside, common sense could also tell you that you could maintain independence, work harder and longer to obtain individual reputation and prestige.
Autonomy and Pride can be motivators. By maintaining his independence he has full control to do what he wants, when he wants. He doesn't need to adhere to anyone elses agenda but his own. These values are known to motivate individuals, in fact they fit in with Maslow's "Self Esteem" need on his hierarchy of needs.