Thickness of guns really only means something for concealed carry.
Concealed carry is a relatively recent phenomena, and an American one at that. A German/Swiss company with their mainstay products designed when disco was king obviously not going to be on the forefront of that. Now, even their newer designs (I'm a fan of the P250) are still pretty thick. I'm guessing they weren't designed with concealed carry in mind. Now, the P238 and P938 are obviously a different story, but their time honored metal framed guns are heir to a different line of thinking.
It isn't all that long that we've been seeing an emphasis on semi auto platforms designed expressly for concealed carry, and it looks to me like it's really the American companies taking the lead in that market segment.