Lots of different factors including the type of rocks in the substrata and rainfall... Copy and paste the link below into your web browser (not Google search)

http://bit.ly/KYNNpu

As Moongrower says, it is simply down to geology. Many of us live on land with underlying limestone, which was made from thousands of small sea creatures with shells. They are mainly calcium carbonate which is limey or alkaline. For those living on granite, or old volcanic rocks, they are predominantly acid or neutral.
The other major factor is whether your garden is old forest or marsh land which is peaty because of centuries of leaves or dead vegetation building up on the surface.
As someone who has always gardened on lime, I am envious that the best flowers and shrubs seem to be acid lovers, but as a vegetable gardener, an alkaline soil is always better.... though you can't grow blueberries!

Even that water we drink here is slightly acidic as it runs through peat and off granite mountains... wonderfully soft though I never use fabric conditioner on anything.

lucky you MG i have always been either on limestone or chalk. both quite hard and definitely needing softener. but the water tastes nicer.

Not sure I agree on the 'tastes nicer' SBG our water tastes great!

nah when i was in scotland a couple of years ago non of us liked it :o)))))) now a drop of whisky improved it no end :o)

But where were you in Scotland? It is a large country and the water is very different in different parts of. You polluted whisky with water?

Acid , Alkaline or Whisky? ...............Love Acid plants love Alakaline plants........Bloody love Whisky Thanks all LOL.