While I get your point and have been in a similar position myself as the interviewer, the longer I've been working the more I think "creative" is just as much of an overloaded and under-defined term as "smart". These days I just look for the ability to think through complex things methodically, and the creative spark will show itself later, and in place of innate creativity, the ability to churn through lots of ideas when it's needed is a serviceable substitute.

And if by "creative" the interviewers (not necessarily you) mean the ability to come up with novel but compelling ideas, that's something that happens on timescales longer than an interview and certainly not under interview pressure. The people I know who are best at generating novel, compelling ideas do it on the timescales of weeks to months.