jbayabas - 3:06 pm on Aug 9, 2013 (gmt 0)
Although the "sexually gratifying" part is still very subjective.
I don't think swimsuit pictures are adult per se. I've photographed models in bikinis and speedos, and adsense allow them. It's the person's pose - suggestive / sexually gratifying - that is not allowed. Though I agree with you, this can be very subjective, especially if the photograph is artistic in nature.
Swa66 may be right:
The real problem behind that is the overly conservative mentality (for what's Google concerned in the USA) that's only growing and becoming far worse.