Iowegian
My preferred turkey size is 20 lbs. I've cooked them in both the oven and the roaster. The reason people use roasters, and have used them for decades, is to free up the oven for other things like pies, broccoli cheese casseroles, dressing, etc. I usually do pies and casseroles the day in advance but the dressing and casseroles have to be re-heated which can take over 1/2 hour. Most people like to time their holiday meal to come together all at once: make gravy while the turkey rests for a few minutes while also cooking dinner rolls and moving the casseroles and dressing to the table right out of the oven, etc. Cooking turkeys, hams, and roasts in a roaster is easy and people in the know do it all the time, no duress needed. As with anything else, if you actually know how to use or do something, it is easy and can make life easier.