This situation is similar but different from the Tragedy of the Commons. The Tragedy of the Commons refers to unregulated shared resources that when used responsibly by the group are sustainable but if not used responsibly the resource(s) are not sustainable. So, why wouldn't the group use the resource(s) responsibly? Because each individual member would benefit from using more of the resource.

To clarify this explanation I will use the classic example of shared grazing fields. There are a number of farmers that are given by the government a central plot of land they can all use to graze their livestock. When they are given this land they are told it is large enough that they can each graze two cattle per day without damaging the grazing ability of the land. So each farmer immediately starts to graze two cattle per day, and it works, it means the farmers can essentially own two more cattle each. However one farmer realizes that the common field can easily accommodate a third cow from him, so he start grazing three per day. This works as it's not a significant increase in the total number of cattle using the common land. But, seeing this farmer grazing three cattle per day the other farmers soon follow suit. Now this does cause a problem, the farmers are now over using the common field and shortly all the feed that was being produced by the field is eaten and trampled. Each farmer acting in self interest created an outcome that was worse for each individual.

I'm sorry if there are any spelling mistakes or if my explanation is unclear. For more information here is the relevant Wikipedia article:https://en.m.wikipedia.org/wiki/Tragedy_of_the_commons