There are plenty of legitimate purposes. I use it to disable keepalive for POST requests, redirect to https:// https:// for browsers known to be able to establi

There are plenty of legitimate purposes. I use it to disable keepalive for POST requests, redirect to https:// https:// for browsers known to be able to establish a secure connection, whitelist tor browser bundle, detect behavior of Accept: header, which differs even between browser versions, and some other things.