The architecture of “not bad”: Decoding the Chinese source code of the void

English does construct things this way, maybe just not with the frequency of Chinese. In fact, "not bad" is a common expression.

That said, it's true that certain flavors of US English, like marketing speak, will avoid many phrases in this family.

This is because many American English speakers will see expressions like this, particularly when not used in a directly complementary way, as either bureaucratic and avoidant or slightly pedantic or both. Because for many Americans, leaving ambiguity implies lack of confidence in the statement or evasiveness. (At the same time Americans also know not to trust confident statements - they are separately known to be "snake oily" - but we still tend to see marketing that avoids directness as even less trustworthy.)

So this mode of expression is much more common in personal speech.

Kids in the Pacific Northwest use litotes constantly, to the point of annoyance, and possibly more often than they use the straightforward positive. Everything is "not bad" or "not great" or, if really bad, "super not great." I've always taken it to be a kind of avoidance of confessing one's real feelings.