Children's exercise - FFS!

I've been annoyed with this children's PE debate since the last election. I just don't understand what the problem is in delivering 4 hours of PE a week for Primary school children.

Now, admittedly I went to a school with rather low numbers but I suspect the problem here is not the supervision, but what actually constitutes PE / exercise and how it could be undertaken.

In Primary school my teacher regularly took the entire class to the gym hall where we played wee games for 45 minutes. You didn't need to get into shorts and t-shirt for it.

We played rounders, tig, crab football (where you could easily tell who was in the cubs and who wasn't) and learned to skip.

Sometimes we had an old guy who could play the piano a wee bit. He came along and we had a mini-choir session, then we did some dancing - which as far as I'm concerned is about the best exercise their is... don't believe me? Check out the professionals on Strictly and ask any of the celebrities who make it through the first few weeks.
You could have a dance in your classroom if you just shoved some of the desks and chairs to the side for a wee bit...

So who is it that's not able to deliver some exercise to the children as part of a fun filled daily education?

Is the problem defining what constitues exercise? or is it teacher's inability to think outside the box or is it that the inner city kids are crammed into some shoebox where swinging low, never mind a cat is impossible.

What's the bloody problem?