Simpson won his first major tournament with steady play last weekend, taking the U.S. Open by one stroke with a 72-hole total of 1-over-par 281.
However, with the British Open scheduled for July 19-22 and his wife expected to give birth to their second child about the same time, Simpson is opting to stay home.
"After winning it's certainly a little harder not to go because I'd love to go and try to win another major," Simpson said at the PGA Tour's Travelers Championship. "But in the grand scheme of things and grand scheme of life, it's a decision that I know I'll always be happy that I made.
"I'm a guy who loves my family and we're probably only going to have a couple more babies, so I have the rest of my life to play in the British Open. I don't want to miss the birth of the second child. So it's an easy decision."
Simpson, 26, and his wife, Dowd, have a son who was born in 2011.
Simpson tied for 16th at last year's British Open.