Romantic relationships are one of the main plot drivers of sitcoms; and due to the often long-running nature of these shows, sitcom romances are often slow burns.
The longer story arcs across multiple episodes also allow for more time to develop the foundation of relationships between characters, as well as the 'will-they-won't-they' trope which is typified by couples like Rachel and Ross, Jim and Pam and Sam and Diane.
