This kind of thing is happening for one major reason - lawsuits, or fear of them.
Most teachers would be fine with letting kids play tag etc, but parents (most people in general) these days carry their attorneys phone number around with them and are quick to pull it out any time they believe their kid is "getting picked on". The trigger word unfortunately is "harassment". Unfortunately, this is the predominate force behind setting up policy for most organizations these days, not intelligence or common sense.
As I said - it's the lawyers' fault.
They are scum who suck all joy out of our lives.