Twenty four of the fifty pictures I found featured the user with at least one other person (twenty seven if you count animals). This would clearly make it difficult for other users to identify the account, making it undeniably impractical. So this use of group photos must have some benefit outside of what is practical. 

People may value their relationships or friendships over ensuring easy identification. Either that, or they value showing off those relationships to others. 

"Here's me with my friends!" they're saying.

"Here's me with my girlfriend/boyfriend!"

"Here's me with my horse!"

One could draw a number of conclusions from this. A more extreme example would be that even presenting one's own image is not a solitary activity, but one that must involve others. It is a social media platform, after all. Of course, it may be the case that the users simply liked how they looked in those group photos. 

Below is an example of one of these photos. Whose profile picture it is is anyone's guess. Although, we now know they like wrestling.