Dating sites have given people the advantage of being relatively anonymous.
The kind of rejection that you may face on dating sites is a lot less difficult to deal with than the kind that you would face from someone in real life.
On the contrary, you may get so much attention on dating sites because the same guys who would have ignored you in real life, are a lot more bold in sending you messages on dating sites.
Dating sites have made it easier for guys who would typically ignore a girl that they are attracted to in real life, to actually approach her through cyberspace.