First, you need to realize that what you see on TV is not real. The situations are manufactured and the people are actors playing a part. They may be professionals or amateurs, talented or hacks, but they are all actors. Do not expect real life to be like a TV show.
Second, you say these people are in their 20s. They are quite young, and romantic attraction is new and exciting. They have energy and enthusiasm. This is good, but it is not lasting. "Lovey dovey" as you call it, is like a candy bar. Delicious! We love candy, but it does not provide the nourishment our bodies need. Adults are expected to understand this, while children often do not.
True love is commitment and sacrifice. True love is a husband holding his wife's hair when she is throwing up, or a wife cooking for her husband's pleasure instead of her own. True love is working together when life is hard.
Invest in true love, and the "lovey dovey" will come with it.