You don't need a Steam Key to play Elite Dangerous through Steam.
There is very little significant difference if you simply add Elite Dangerous to the Steam Library as a Non-Steam Product. The Steam-Overlay works, the Steam Friends/Contacts works. Auto-Updates are irrelevant since the ED Launcher handles them regardless.
People demonizing steam... and yet ignoring the advantage Steam provides from having created a huge consumer base upon which to pitch your product too. +10 years in the making. Why shouldn't steam share in the profit of a sale they helped make possible by being "Steam"? Do we seriously think that the influx of ED sales is solely composed of players that already knew about the game?
Steam is out there 24/7 putting your game in front of the eyes of 6 million gamers every day... Something Frontiers web-portal isn't doing. So why not share a spiff on every Steam purchase with VALVe?
Everyone is so concerned about the big bad Steam monopolizing all the profit from each sale of E

...
yet... no one seems to care that David Braben marked up his game to $69.99 when he released it on Steam... what other game has ever done that? I'm sure it has nothing to do with the realization of how lucrative Elite Dangerous being on Steam would be. Feels like gouging to me. Forcing your fans to shoulder the burden of paying an extra $10 to play your game on their favorite and preferred digital platform.
Top Selling Game on Steam right now...
Yeah, this was a "bad idea" alright. I'm sure the incoming torrent of revenue is causing so much distress over at Frontier right now.
Oh... but Steam is getting a percentage of all this new money that is suddenly pooring into our ledgers! How miserable! How ever shall we cope? Our only solace is that we can use all this money to dry our tears.