The three cats decided that they had enough and sat on the ground to call it a day.
Hunting mice was something that they have been doing throughout their life.
In fact, as long as there were mice on Earth, they would never stop hunting them.
So, I guess there is nothing wrong with those cats taking a break once in a while.
Even people who are ever so busy need to rest at some point, and when they hopefully retire, they want to have some form of pension, lifetime savings, or similar to rely upon, when they will be no longer as active in life, as they used to be in their youth.