This is very normal and how most business works.
1) common
2) according to social norms
Neither of which are actually the same as ethics.
I'll make a slightly stronger argument though. You should do business with those you trust. There is no rigorous rational way to determine someone's trustworthiness, so you must get to know them and see how they respond to situations and ultimately rely on your intuition for making decisions.
A good example is a new startup giving an executive a free account to try to get their interest. According to you, it's unethical, but it actually helps small companies compete.
Silicon Valley created its own pedestal of "meritocracy" so when we find out that it's no more meritocratic than any other business-- and, in fact, often less so-- the black eye is deserved.