I don't have a dog but I do walk my sister's when up in Scotland.

She (and I) are firm believers that poop should be picked up whether on the pavement, on grass verges, in parks, in nature reserves and even in the back garden. There's nothing more unpleasant than you or your dog walking through grass and skidding on poop. And completely unnecessary - it's not that difficult to pick up in a plastic bag and dispose of accordingly.

On the lead front, I do think it depends. Her dog is leash on while walking anywhere near a road but he is allowed 'off' to run around in parks etc. Having said that, it's only in quiet parks where there aren't lots of people around to knock over or kids that might be scared. And if she sees people up ahead, she'll call him back to heel in case they're nervous. And he's a bouncy, friendly retriever as opposed to something aggressive with drooling fangs... ;p