Disabled badges arent handed out with free bus-passes you know saslou....
Older people are more likely to experience some form of disability, often invisible ones. A wheelchair does not a disabled person make.
My MIL has a badge because she has chronic emphysema and can't walk far without getting breathless. FIL has his own badge because he has chronic arthritis, is almost completely deaf, and has had cataracts which didn't go away properly when they were operated on. (Yes, i know what you are thinking - just shoot the poor bastard now, but seriously, he's actually quite a happy chap )
People with physical limitations, whatever they are, take priority over everyone else. Including parents with their PFBs. That's not to say that shops can't make life easier for parents by allocating wider parking spaces, and making them closer to walkways/the shop. I always really needed a parent/child space because my child had a propensity to escape from his harness/pushchair/whatever and dash across the carpark. He actually got hit by a car once (thankfully he bounced off, but unfortunately he now thinks he's invicible ).
I should have just said "get a grip" at the start of this though, really, shouldnt I?