A team of researchers published a study in the Personality and Social Psychology Bulletin that say couples who have very high "relationship visibility" (or publicly post a lot about their relationship) may be masking relationship insecurity.
The researchers thought that people with avoidant attachment styles (or withdraw from partners) would have less desire for "relationship visibility," while those with anxious attachment styles (or need more reassurance from partners about the relationship) would have a higher desire for visibility.
"On a daily basis, when people felt more insecure about their partner’s feelings, they tended to make their relationships visible," the researchers wrote. "These studies highlight the role of relationships in how people portray themselves to others."
Other research tends to suggest the same thing — couples who post a lot about each other may not be as happy as their polished Instagram presences make them out to be. It may actually be quite the opposite. I am willing to bet my salary that you're thinking of a specific couple that you hate-follow who always posts incredibly detailed updates about their relationship, and finding validation in these findings.