bottom of door to floor clearance

When we went to have a peek at our house earlier this week, we noticed that they have put what I can only explain as a draft stopper brush strip (which you usually see on the bottom of a front door) onto the bottom of the bathroom and laundry doors (internal doors).
I've never seen this before and was wondering if anyone else has this in their house?
From reading the Building Standards and Tolerances (thanks jamiet) it states that the gap under a door should not be more than 20mm with floor coverings laid. Would it be that the builder has seen that the gap is greater than 2cm, and put this on to fix the problem? Is this an acceptable solution?

I personally don't like them...

Ray.

This is a little OT, but when we moved into our current house it featured hideous shag pile throughout. The first thing I did was have it all ripped out and the beautiful Tasmanian Oak floorboards polished. But now we have huge gaps under the doors. I might take your idea and put in some draft stoppers. Just need to find some subtle ones that won;t look weird on the original 1920s doors.

It will be to stop air movement - these rooms need to have ventilation, and without the brishg strip air movment would be greater, and the rest of the hosue will be cooler.
I'd be tipping it is a basix requirment somewhere.
Steve