why do people fall in love with married ones?

Answer 1

For the same reason people fall in love with single people.

Only if the married ones are taken... Then they should leave well enough alone...

Some people like the challenge, like to cause conflict, trouble makers, some people may not know the person is married and fall in love only to find out later that they are married.
Or they just find that person attractive and cant resist their feelings even though they know that person is married.

~faith

Answer 2

The better ones are taken. People can't help who they are attracted to.