I know, it seems daft that so most agents and publishers don't accept email submissions, but the reasons I've gathered are usually an assortment of the following:
you can't read email submissions in the bath, on the bus, in bed, which is where agents and editors do it; the one place they never have time to read submissions at is in front of their computer
you can't scribble on the margin of an email submission
you can't stick it through a photocopier to hand out at a meeting so that everyone else can do the above
printing things out is a pain - how often have you sworn at your printer? - as well as expensive. The average submission of sample chapters gets about 90 seconds of reading, so they're not going to spend 5 minutes printing out each of the 400 submissions they get a week
it's easier to forget about an email submission in the depths of your inbox than it is to lose a wodge of ms (though they do that too, of course)
it's too easy for aspiring writers to do mass submissions of totally unsuitable work by email (and believe me, they do), so the fact that a writer has to assemble all the bits and stamps and pay for the submission makes them concentrate a bit harder on whether it's worth sending.
Getting the submission right and in the post and stamped and addressed and self-addressed is a bore, but maybe one should think of it as a sign to an editor of one's seriousness
Good article here:
From Post Box To Agency Inbox:
An Insider Look At How An Agent Reads and Evaluates The Requested Sample Pages For Your Novel
which does what it says on the tin. And a list here
Agents That Accept Email Queries
of US agents who nonetheless accept email enquiries. Bookspace seems to be a good site all round, in fact.
Emma