Are there really that many acts that can be counted on to fill venues that big around anymore? I think I can count them on one hand.
Shed shows will probably go the way of stadium shows in the next 10 years.
There may be two or three tours in sheds per year but their days of being the norm are numbered IMO.
It may also have more to do with the internet making more music accessible to the public, fragmenting the public into smaller niches than the inability of people to afford bigger shows.