mostly single people who are seniors are bad co-workers. This is so common, they can put in extra hours, work on the weekends etc which a family man cannot!
Wonder what makes you feel putting in longer hours, after hours makes a person to be a bad coworker. After all, the argument could be turned around and said folks who are married are more 'greedy' thanks to their position and usurp opportunities. I do find most single persons are trustworthy and dependable for a work situation. Jai Hind.