Because of justified fear as to how family, friends, neighbors, co-workers and people not even known may react when they find out a person is gay. Some common responses are scorn, derision, anger and insults. Other common ones are lack of job opportunities, hostile workplace, being fired. A less common response, but still one to be worried about is violence.
Such fears have lessened significantly over the last 20 years, but they are still valid fears. Just look at some of the comments on this message board.
Separately and somewhat ironically, I always assumed you were gay and kind of wimpy, judging from your posts.