I think the answer is pretty clear. A couple main reasons. First the actual game play is very limited and game mechanics have tons of bugs, physics are broken and random deaths can happen at any time for no good reason. Might as well ensure the most basic thing of all (the one that is probably the less exposed to critical issues), i.e. moving from A to B, is as long and drawn out as it can be. Second, such long and unnecessary "walks" are explicitly designed to lie to the player, making him think the game is much more of what it is, telling him there is tons of areas to discover and interact with when in reality 99% of what you see is dead and can not even go there.
It is clear, each gameplay of 1 hour you really use 10 minutes of something interesting. You can say that you have been playing SC for 5 hours but it is a lie, it has really been 50 minutes of real game and the rest of the time you've been wandering around doing nothing interesting.
But your argument sadly has a flaw; You don't take into account the non-existent killer elevators, the deadly stairs, the trains that throw you into the void when you try to get on them...
And when you've managed to escape all that, and you're with your ($200) supership, you're starving or thirsty because you forgot to buy a snack and a soda between platforms and trains. Yes, starving to death in a meaningless and unfinished supposed "survival mechanic", that no one has asked for, that makes no sense in this type of game, and that gives nothing positive and much negative.
Realism... immersion... can you call a lawyer to get you out of jail because you think the crime you've been locked up in Klescher for is a lie? Or file a claim with Lorville Hospital because you think they have charged you too much for medical treatment? Can't you? Bah, how unrealistic...
The limit of how realistic we want our game to be obviously has to be in the technology, but also in the gameplay and, of course and more importantly, in the development time that it implies with respect to what it offers playably. CIG don't know how to handle that, it doesn't care, the only thing they want is to incorporate unimportant but "cool" things that they can gradually incorporate because they don't need any core technology to work. And they do that because they can't put out more things that are needed by mainstream technologies simply because, after 10 years, they still haven't managed to do it.
By the way, speaking of the "realism" of Klescher, a "real" prison, with a "realistic" mechanics... where EVERY DAY thousands of prisoners escape queuing through a corridor of tunnels in a cave and the authorities do not notice (can anyone fix that damn hole in the blades?), all this by stealing a code that is very big written on a screen in jail... Incredibly realistic... wow. Well, the SC prison is like the nonsense of the train, or the hospital, the "hacking" of the Comm-links, removing the criminality in Kareah, etc, or the rest of the current mechanics of SC; a nonsense that makes you say "wow" the first time, but the eighth time you realize that it is very boring and repetitive, and that it really does not hold up at the plot level if it is done in an ordinary way (please, someone put a bloody security group at the "hole/entrance" of the Comm-links... the people hack us 500 times every day)
And I'd rather not talk about the "secret compartment" of the Mercury Star Runner ship... just copying the Millennium Falcon to make people say "wow" again. Very well, if you remove the queen from the board and put it in a coaster, you open the secret compartment... and?, everyone already knows... the rest of the players are NOT going to be fooled because they already know, and that mechanic doesn't make sense to use against AI (Did someone say AI?). It's ANOTHER stupid and pointless mechanic. If nobody knows in advance that this compartment existst (as happens to the Millennium Falcon) then perfect... but anyone can have a Mercury, it's not something special, it's a "secret" that really isn't a secret, and that loses its playable and plot value at the very moment of birth.
But of course, with that stupid excuse that it's a "smuggler's" ship they can sell it to you for $260 and justify its supposed "role" which is false because that role doesn't really exist in the game yet.
Realism and immersion...