One thing I have found is that if you have a large dataset, the standard error can become so small that any difference in average performance will be significant. Obviously not always the case, depending on the size of the variance etc but I imagine it might be why it’s often acceptable not to include them.
If the number of injuries is solely down to too many games then it’s down to the managers to control that. After all it’s the managers who put the players on the pitch.
A lot of the bigger teams complain about the Carabao cup but it’s the once time the sides outside the top 6 are in with a chance of winning anything. It just shows how greedy the top 6 are that they would sooner get rid of the competition than field a weakened team and have someone else win it.