As for Alamy and RM as Editorial, the reason is simple cost!
A newspaper not like advertising often just require a small spot size image for a single topical use, and RM often works out "cheaper than RF" for the specific use.
Alamy sells about 76% RM and 78% Editorial so uploading as RF could lower the chance of a sale at the moment, but this may change over the next 18-24 Months.
Alamy are opening a US office and are looking at the US advertising market, even though Alamy is not know well in the US at present 30% of Alamy Sales are to the US and 21% of photographers are US based, the editorial US market is tightly sewn up already, and Alamy will be moving to Photographers uploading model releases this year sometime, this is to cater for the USA Commercial marketplace.
David