[eaevans99]

Here is one answer in the form of an analogy -- but I preface this by saying that comparing the set of all academic science with the set of all industry science is fraught at best -- academic science is to cottage industry as industrial science is to factory production.

A related consideration is that training grad students and post-docs is a key component of most academic science. The requirements of training often limit the size of teams working on a single project with the PI-trainee relationship dominating the organizational structure.

As the "PI" of a science startup R&D team, I can start and stop new projects at will with varying team sizes and mandates without the consideration that my folks need to produce a body of published work to further their careers.