Well, I think it is simply the fact, that everyone desires happiness and love is often enough source of such great happiness, that we seek to find and keep hold on.
Of course there is always the chance of getting hurt, but that is with everything in our lives that make us happy, because to everything there is a contrary, mostly just losing that specific thing whatsoever that made you happy in the first place.
As we know the greater the happiness, the stronger the pain, it is to us to decide how much happiness we can take, to bear the resulting pain.
If we avoid any pain, we avoid any happiness and that would be a try to live in indolence.
So, if it is seen like that, it is a matter of strength how happy one truly can be.
And yea right, I think 'love' is not what most people think, something for the own advantage, but a matter of 'giving', no matter how f*cked, not 'receiving happiness', but hey .. whatever explanation you prefer.
[that might be taken wrongly, don't know how to explain it, right now .. dontgetit]
(sorry, I am tired, so .. off to bed now and way too lazy to correct those phrases I'm insecure about .... I suck at English lately 😛)