"you will probably not meet, and be happy with, someone you meet in a dive bar, or online dating. it's just common sense" Huh? Since OkCupid, and many others,

"you will probably not meet, and be happy with, someone you meet in a dive bar, or online dating. it's just common sense" Huh? Since OkCupid, and many others, work and are very popular, how can it be common sense that you won't meet someone you'll be happy with? Can you explain that?