Expanding to 24 has in some ways led to this decision. How many countries can host the tournament alone? Germany, Italy, Spain, England France and Russia. I'm not sure Portugal could manage the expanded competition. UEFA don't like the large country FA's being to dominant, let alone of England hostng every 20/24 years, so need a way of spreading the competition. They've tried co-hosting but that means that they need to let in several host nations as top seeds.
Perhaps a better compromise would be to allow bids of single countries or geographical groups of cities within a certain distance (e.g. within say 200km of a central city). In doing so you could expand the range of potential host areas and keep it intimate for fans. Cities from Holland and Belgium could get together with cities in northern France (e.g Lille, Metz) or western Germany (Dortmund, Dusseldorf, Cologne). The Scandanavian countries could get together and create a local tournament based on Oslo, Gothenburg, Copenhagen, Stockholm and Malmo (perhaps going as far south as Hamburg). The cities of the Baltic countries could get together with counties to the south (Greece), East (Bulgaria, Romania) or north (Hungary). Or Vienna, Prague, Bratislava, Budapest and Zagrab are all within easy travelling distance. Many of these arrangements would be more compact than a tournament in France or Germany. Most of these countries are (or will be) within the Schengen Area so travel across borders would not be a problem. If it was based on cities then you wouldn't need to invite the hosts, although perhaps favourable seeding in the qualifying rounds could give them a better chance.
