It takes courage to get what we want in love.
There's a reason the climax of most romantic comedies is hinged upon the main character finally getting the guy/girl of his/her dreams. That moment when they both knock all their cares to the side to begin making out passionately is so electric, so deeply satisfying, even though we can see it coming a mile away.
This is especially true if we have been watching the protagonist struggle with telling the object of her affection how she feels the whole movie. As spectators, we're elated for this fictitious character, not because we're that obsessed with her, but because we know what's on the line.
We know what it feels like to put all your cards on the table just for the other party to say, "Oh, no thanks." Requited love is as exhilarating as unrequited love is devastating. And there's no greater emotional risk than stepping up, declaring your love, and waiting for an answer.
Contemplating that act alone leads to all sorts of anxiety and, in my case, straight-up terror.
Sharing a chunk of yourself is already showing vulnerability. If someone laughs after we share our deepest desires, we don't get hurt because that person invalidated our feelings; we feel hurt because we trusted someone else with a part of ourselves and it wasn't honored.
Professing your love for someone is like that times a thousand because you aren't just telling someone your objective feelings about something; you're showing them your heart and inviting them to share it with you.
Even worse than someone outright rejecting your heart is someone who will see your love and decide to use it to their advantage. Instead of setting you free to find someone else to share your heart with, this person will steal your time and energy while giving noncommittal answers about how they really feel about you, which is akin to prolonged torture.
A severe "No" might shatter your heart initially, but it is nothing like the slow-burn agony of being lead along by someone who ultimately doesn't want you in the end.
So it makes sense that we put our energy into cheering for fictitious movie characters to find love; it's far less risky and, no matter the outcome, we're still going to be able to sleep at night. (Example: Julia Roberts got rejected by the man of her dreams in My Best Friend's Wedding, but it's still a classic rom-com because "Hot Mess Julia" is the best kind to watch.)
This being said, when the credits roll and your life is in the same place it was two hours prior minus some popcorn, the real message to take away from any romantic film is that it takes courage to get what we want in love. Vulnerability isn't a bad word; it just means that you have to gather your strength, and regardless of the outcome of your professed affection, keep the faith that you'll emerge stronger from the experience.