Comment 22 for bug 556293

I strongly disagree with that idea. Reading from /etc/environment means that user-specific proxy settings are lost.

Not letting apt receive the environment properly from its parent also means that you can't set up a temporary environment where all web fetches ought to go through a proxy, when you don't want fetches from other shell sessions going there.

Having apt get its environment like every normal program does seems important, to me, and doing so would seem to necessitate sudo allowing http_proxy through.

On the other hand, perhaps it's not a terrific idea to always allow http_proxy through, in case the user is unaware that it was set out from under him (potential security problem?). Is that the reason you're reluctant to alter /etc/sudoers for this?