Yeah they don't have to, though. I agree - Westfield came to us and said "You should spend $1800 a month on a billboard at our mall!" We came back with "can you show us some metrics and demographics on your foot traffic?" and they said "No! We can't! No one has ever asked for that before! You should feel bad for inconveniencing us with your claptrap! This $1800 offer won't last long!"
But there's nothing inherently wrong with the concept of a permanent public market.