Economical activities ought to be a means to advance society, profit should
only be an effect of providing a service to society; companies or individuals
who seek otherwise do a harm to society (almost all of them). Proprietary
software may be more profitable because it generates artificial scarcity so
that the developer then can economically exploit it, not because it provides
an higher benefit to society. Proprietary software is like selling rotten
food to people so that they will first pay you for the food, then again for
the medicines.
Here are some examples in the economic sector of informatics: Thinkpenguin,
and Gluglug are committed to provide a real service to society. Facebook,
Google, Microsoft and Apple are only interested in serving themselves,
sometimes they serve society, and very often they harm it.
I interpret your question “why would they?” as “what motivation do they
have?”: the answer is that they should avoid proprietary software because
it gives an unfair power to their developers over their users.
They do not “have to appease to enterprise clients who want more support
and perks than CentOS”, they chose to do so, and therefore it is not a
justification for ignoring ethics. See also the essay “Have To” Is a
Relative Phrase.
