I'd love to see a pic of one of those Brit leaf blowers that come with a collection bag...that must be an interesting design...
To be honest I'm not that familiar with leaf blowers, I've never owned one.
I've seen them being used though, and to me it seems utterly pointless blowing leaves from A to B, only for the wind to mess your work up, as krich pointed out!
Now if the leaves were being collected, similarly to grass cuttings for instance when you mow your lawn, then I'd understand it, you'd be cleaning a mess up, instead of just moving the mess, only for it to return when the wind blew!
However, the impracticalities of installing a leaf collection receptacle on the blower itself are numerous. I understand that.
Me? I'll stick to leaving the fallen leaves where they are and let nature do it's thing.