I've used an accent in approximately half of the roles I've played, usually Indo-Pakistani. As a minority performer, I'm often called upon to play foreign or immigrant characters who would naturally have an accent. And as long as the part is not demeaning or stereotyped, I'd rather do it than not.
But more often than not, the accent is required for a part in a Canadian show and unrequested for American!
I once got cast as an air traffic controller from Mauritius in May Day, a hugely successful show that recreates air disasters. My character was a Mauritian, in Mauritius. Mauritius is in the Indian Ocean and their citizens speak English with a very distinctive accent that is a combination of Indian languages and French. Very interesting and challenging to pull off. Shortly around the time I got the part, I bought some pants from a store salesman from Mauritius. So I worked hard to remember the music of his accent and apply it to my part.
Luckily, a friend of mine was the AD on the show and I eagerly mentioned that I was working on the accent and would have it down by the shoot day. Then he called me and said that the word came down, NO accent. The show was seen on science type channel in the US and their audience wouldn't tolerate things like accents or subtitles. So my Mauritian air traffic controller spoke like a guy from Toronto. Oh well.
On the other hand, I find that on Canadian shows, I'm expected to have an accent in the interest of multiculturalism, I guess. Not sure why this is, but having surveyed my resume, it boils down to Canadian shows prefer the accent, American shows do not.
Regardless, being able to pull off an accent makes me more employable. It's absolutely essential for me to make a living, but I daresay Anglo actors who can do accents are also more employable.