Why did Jesus teach love?

If you read a good part of the gospel, most of the time the recurring theme is all about faith, hope, and love. According to 1 Corinthians 13:13 - And now these three remain: faith, hope and love. But the greatest of these is love. But why did Jesus teach love most of the time if we humans really are capable of loving. We have the potential for love but why must Christ emphasize love to man?

If you were a man devoid of any knowledge about the gospel, you would in all probability, love only those you want and not love those you must. Even people who were taught the gospel are also the same. Jesus taught us to love our neighbors as we love ourselves. When he was asked who our "neighbors" were, he told the story of the good Samaritan. In essence, our neighbors are the people that we meet everyday and not just the people we interact everyday, nor are they just our friends and love ones. Look at this example:

LUKE 10:27 NKJ
So he answered and said, " `You shall love the Lord your God with all your heart, with all your soul, with all your strength, and with all your mind,' and `your neighbor as yourself.' "

We are indeed capable of love, but we don't exercise enough love that we just tend to love the people that are easy to love and we shut out (even hate) difficult people. That's the reason why Jesus had to reiterate his gospel. The commandment is to LOVE but we choose to love only those we can.