grasstreeleaf perhaps people don't want something vaguely unsatisfactory (a pie lid without the rest of the pie pastry) regularly - they want the meal they ordered (an actual pie), but eat it rarely.
And perhaps, like me they do. I often think fully enclosed pies don't taste as good, the pastry turns to stodge underneath as the gravy melts into it.
Sometimes those places do have a limited light bites/ smaller appetite menu, a children's menu of junk deliberately not meant to appeal to adults and often restricted to under 12s, and a starter menu, but it doesn't make economic sense for them to offer the full menu as half portions as discussed already.
Yes and typically the lite bites are aimed towards pensioners. I just think it is rather dysfunctional, why as a nation do we think it acceptable to offer only junk to children and smaller meals only to pensioners? Why not just have different meals which anyone can chose to have?
to provide half portions of entire menus which will reduce their already usually tight profit margin if offered cheaply, or be considered poor value and provoke complaints if priced close to full standard portions.
People could eat out twice as often if the meal had a more normal calorific load and as for higher preparation time a lot of the extra salad a veg comes preprepared anyway.