Yes it is imperative, because we've been flying around for the last 3 years, staring at the same uncustomizable HUD which is the same in every ship.
Braben said his original vision for Elite is that we're people in a real futuristic setting, not just a ship.
Do you know how boring Mass Effect would be if we could only sit in a chair and stare out a window in the cockpit of the Normandy?
The first person view is a major factor, it really changes the way people experience the galaxy. Because it gives a proper sense of scale. First person gameplay is more personal than sitting in an SRV or looking over your shoulder in a cockpit towards other players.
How often does a player walk around in Mass Effect? If they can't imagine meaningful gameplay they only need to look at Mass Effect and other scifi games with EVA. Mass Effect received more awards and higher ratings and sold millions more copies.
Mass Effect 1 and 2 sold more than 7 million copies. Elite Dangerous won't come close to that without EVA.
Thing is of the 2.7 million copies sold of Elite Dangerous... only a small fraction are still active players. That's why 2018 is focussed on improving the core game and better meaningful multiplayer (wing missions, squadrons, fleet carrier) etc. Otherwise the remaining player base (and source of income for Frontier) will leave as well when the next space sim appears that will challenge ED. ED will have more difficulty to retain those players if doesn't have atmospheric landings, space legs etc.
There are more space sims on the horizon. There's X4: Foundations which will include space legs from the get-go plus the management style features which have been lacking in ED since launch. Dual Universe has a deeper player driven sandbox where people can build all sorts of things.
Infinity Battlescape (has player controlled capital ships, large planetary structures, atmospheric planets).
So I don't want to sound like Nostradamus, but Frontier has to add something major, something huge and jaw dropping if it wants to retain its leading position, retain and expand the player base.
Sure multiple games can exist in the same genre. It's about retaining and expanding the player base and that ED doesn't face a massive decline in the near future when those other games move into the same market space.