Are jeans sensible fieldwear?

One thing I noticed amongst the students on last week’s trip was that a fairly sizeable proportion of them were regularly wearing jeans in the field.

You are unlikely to see British third year geology students opting for denim in such large numbers, because it is likely that one of the things they learn on their first year excursion, which commonly takes them somewhere in Scotland, is that wet denim is extremely good at both weighing your legs down and sucking every erg of heat from your body. The friendlier climate at these latitudes may mean that the offenders in the above photo have not had to endure this lesson, but surely they would have experienced the clammy stickiness caused by wearing jeans when the temperature is high, especially when scrambling up and down hills in the heat of the day. Perhaps I’m alone in my opinion that jeans are, in general, highly impractical field wear*, so I open it to the floor. Should any self-respecting geologist be wearing jeans in the field?
*For the record, I usually wear shorts. But then, years of playing rugby in the depths of winter mean that my legs scarcely feel the cold.