Simple really - too many people wanting to use limited recreation facilities.

It is not unreasonable to run your dog over a park.
It not unreasonable to have children riding bikes, and skate boards etc in a park.
It is not unreasonable to want to play ball games in a park.

None of these things are necessarily very controlled, and the more people crammed in, the more the chance of unwanted interaction with others.

So more recreation space is required.
This means we do not sell off and build on existing park land - doh - as was planned with the park on Dartmouth Rd (and I believe Crystal Palace is being eaten into again.)

Golf courses and graveyards need to be very heavily taxed in cities as they use up a disproportionate area for the number of (live) people who access it.
Hopefully this would in time free up more recreation area.