@Tcof
The reason why those who seemingly have no experience with love is because they are able to observe each relationship with open eyes.
Whenever people, particularly young people, are in a relationship, they tend to focus solely on their specific relationship and what they get out of it. They look what they look for in a partner, what makes themselves or their significant other happy and unhappy, and whatever causes a rift between themselves and their significant other. All of these observations are coming from a person in that relationship, and so the outcomes that come from said observations are usually based on what the person wants out of their relationship. So whenever someone whose experienced with love, personally, gives their two cents on relationship advice, whatever he or she tells stems from their own personal experience. Even if the person has had more lovers/partners/boyfriends/girlfriends than your average person, their advice will more than likely be based off of how they've perceived said relationships, not necessarily what those relationships actually were.
Those who aren't as experienced, or the more extreme have no experience with love, are more times than not looking from the outside. They look at what causes two people to fall in love, as well as what makes people fall out of love. And since the person doesn't have any personal stake in said relationship, the person is more likely to be objective in analyzing the many facets of romantic relationships.
It's like how humanity learned the nature of psychology of humans; various, unbiased, observations.