I generally agree with your points, although in the takeout case, the host can probably communicate fairly clearly that they're going to order takeout (because they don't cook, don't want to bother with a caterer, etc.) and if anyone asks what they owe wave them off and that's that. Though, of course, if they did cook a meal no one would think of paying. (Though informal get-togethers with my friends tend to be pot luck to at least a degree.)

Of course, financial situations do matter. Some new grads scraping by in the expensive city are probably not going to operate the same way that generally well-off professionals where everyone knows that a group takeout order really isn't a big deal for the host.