Cormoran: IMO the modern gamer mentality of wanting everything in one play through is one of the pests of modern gaming.
Leroux: It's not a modern gamer mentality, it's just a matter of personal preferences, and I know I had that preference even back in the early 90's. Maybe it's a bit more common now, because there's such an excess supply of games and because time is more precious for adults than for kids. I get why it annoys you and I agree that joining all guilds at the same time is kind of silly, but from my personal point of view hardly any story-telling game is worth the time investment of playing through it twice, just because some parts will be different - there will still be more repetition than new discoveries in most if not all cases, and I just don't enjoy that, never did.
Anyway, to prove that it's a pest of modern gaming, you'd have to name a lot more examples than just the Elder Scrolls series catering to it.
I don't mind going through the parts that are actually very different on the 2nd or 3rd run through. One thing I can't stand is going through the boring tutorial parts again, just to see the different aspects in the middle to late parts of the game.
Edit: Games like Fire Emblem and SRT avoid this by allowing you to focus more heavily on other characters you may have overlooked on your first playthrough.