It's been a planned feature from the beginning and it's something a lot of people want included (I certainly do).
Other than making the game generally more impressive and attracting new players, walking around opens up new gameplay avenues such as;
- Exploring your own ship and seeing all the customisations you've added
- Exploring stations & outposts and meeting other players face to face - this could improve the social side of the game
- Hostile ship boarding/defending (my favourite) - potential for stealing valuable materials.
- Station combat - could add meaning to 'civil war' and 'war' states, stations become more dangerous during these times
- Exploring wreck interiors (space & planet) - will be quite tense in some of the larger ships, especially when aliens are in the game.
- Potential to make the black market aspect of the game more interesting/dangerous if you have to go off and meet shady contacts in stations and risk arrest from the authorities
- Potential for criminal players to be captured alive and taken into custody (possible bonuses to bounty payouts)
Those are just the first things that sprang to mind, there are most likely loads more benefits it will bring to the game. I'm hoping walking around is going to be season 3.
Those are pretty cool features my friend, but I have the feeling you're gonna be disapointed. Ponder please for a second how much more gameplay your list would add to the game. I'd tell all the work that Frontier has done so far to develop Elite Dangerous as it is now, you would have to multiply by 10! And now think about how practically little you'd be gaining out of such a gameplay, comparing to the vast efforts it would consume to implement all your list...
There is a reason why those kind of features are being implemented into this *other* game with a budget 10 times higher than the one at Frontier's disposal (yes, I'm sorry for bringing that one up

). But this is also a reason why Frontier is approaching every tiny detail of thier simulation with such care and attraction to quality, as they're investing all their efforts into flying model (the SRV fun is a variation of this aspect as well) not forgetting same time about all the things that are hapening in the background of your simulation experience for you to have an impression of living and evolving galaxy around you. As you see the proper, complex immersion throughout whole Milky Way (!) is everything here.
In Elite Dangerous bright future I see more and more complexity of those features, more variations about them and more variety of the exploration of the void and stellar bodies. Those are the strongest parts of this unique creation, totally exceptionall worldwide. Not socializong with your pilot in the starport cantina and other actions mentioned by you and so much MMO alike. Elite would never be able to provide you such ways of having fun, well maybe if they'd be having 100 mils pounds to spend on their developement process during next 5 years. But they dont and they have picked the best alternative road ever. Providing you and me amazingly unique experiences this *other* game will never be able to provide, as its idea is just way different, the sandbox over there is providing you more actions possible to undertake, true that. But please believe me, when I'd tell you that sandbox is way more shallow than the one at our disposal in here my friend. As you hopefully see one day, the target audience for those both titles are way different. You can totally enjoy both though. Its just you will love only one
Conclusion of mine?
Wanna hang out on spacestation's corridors with your online friends? - have fun with the *other* game, when it will be ready... You might get back to the real space simulation soon after anyways

(okay..., I'm a fanboy

)
Wanna experience the vast, dangerous and mysterious void out there, enjoying the best space flight model there is in gaming indistry and enjoying the breathing, living Milky Way of year 3300+? - keep your sticks tight, coz its gonna be hell of a ride, just not the ride you're counting on, I'm affraid my friend.