To put it simply, love makes people feel good about themselves. It makes them feel like they are appreciated and valued by others and that our life is actually worth living, because we have others to live them for. Also it makes them feel like they can have someone to rely on and trust, which also makes us feel good.
Theoretically, they aren't important since logically and physically, we can survive without love. But humans also have mental health and love is just one of the few things that we need to be mentally healthy.
