My mother refused to get an "ugly advent calendar with bad chocolate, when we can get a pretty shiny one with pictures *and* have all the good chocolate we want every day". (The chocolate advent calendars you could get where we were had the cheapest chocolate available, the gritty kind with 28% cacao.) I had to admit that it was a reasonable argument (good chocolate always is.) Once I got one with good chocolate from my grand-aunt. I still fondly remember it. (And it was only moderately ugly.)
Yes, the chocolate calendars for children have the cheap chocolate in them - but somehow, exactly that cheap chocolate from the calendars is a part of my childhood memories of this time of year. And I'm a milk chocolate person anyways - I guess that if you tend more towards the darker chocolates, those calendars would indeed be very disappointing.