The reasons I've seen given in the British newspapers are the reasons Mea has stated. Primarily security and identification concerns.
There's something of a debate in Britain right now too, as evidently the burqa is outlawed in some Islamic countries, where it is seen as more of a political statement or a statement of absolute extremism. Islam itself requires 'modesty' not head to toe covering.
I can't say that's definitely true, but it's what I've read.
