Yep, they do act younger than Jaime and Ali. At least Ali has managed to steal some intelligent-sounding soundbites from her shrink, even if they are all about her needing to relive her childhood...Anyhoo, I think that another reason is that boys/men aren't generally as open as women are. The pseudo-philosophizing that Jaime and Ali do most likely wouldn't happen with 18 yr old rich males. And if anyone catched that E! story on the uber-rich, the men Paris and Nicole's age didn't have the same spark, the same presence, that Paris has.
Well, I never saw Rich Girls, so I can't form an opinion on that, but with Simple Life, I think that having girls doing the farm work makes the show more interesting. We have the girls going ew and yuck when they have to do something with livestock. I don't think we would have the same reaction with a couple of Hollywood boys. They would probably suck it up and bear with it. The example that comes to mind would be with The Newlyweds, Jessica Simpson goes ew whenever she has to do any cleaning or tidying while Nick just sucks it up (but he is also more a neat freak that she is).
Also, females tend to shop and enjoy shopping more than guys and I read that in a scientific study. I'm a girl and I admit I like shopping (which means I like browsing and looking at sales but it doesn't mean I have to actually purchase anything). While males tend to prefer just buying. That means going into the store, walking to the area, picking up the item, and then purchasing the object and leaving the store. My brother is like that but he actually likes the occasional shopping at the real bargain places. This means that the parts of the shows that show shopping would almost need to be with females because males wouldn't do that.
I saw three ships come sailing in.