Yanks generally get all media on Tuesdays as it then gives a whole week before sales figures/charts are released on the Wednesday.
In the UK it's released on Friday because years ago stuff was released when it became in stock, no set date just chuck it on the shelves. Big retail companies hated this for advertising purposes so they sat down with the supply chains and made it so items would be stocked and released on Friday, meaning they could get adverts out on Friday and get the weekend business.
There is no law to have it on Friday but it's just carried on, also people used to work Mon-Fri so they could look forward to a game on a Friday. That said in a digital era just release the bloody lot on the same day. I also presume for online games it splits the load on the servers.