Because some people are really REALLY obsessed with her. Just look in any thread with Liara in the title. You always find the same few people: Oh, Liara is sooooo creepy. She has a part of Shepards old armor. Stalker!!!!! As I see it, Liara simply keeps a memento that reminds her of Shepard. We know it is not unusual for an asari to keep mementos. The armor is a relic from Shepards battles. Shepard is the saviour of the galaxy keeping his armor is the equivalent of having the space age Excalibur. Nothing creepy.
Anyway, my point was, that I doubt the vast majority of Mass Effect players make such a big deal about this or some harmless hug. That's why I mentioned the review threads for LotSB, which are a better indicator of what non-hardcore fans think about the DLC or, specifically, Liara's apartment.
You're making an assumption (they don't say anything about that), most of the people that mentioned LotSB loved the fight with Tela Vasir more than anything else. Further, initial reviews usually gravitate towards such things, they quiver the nostaglia glands. It's far better to get a sense of how people feel after the glamour is gone, and they look at things with a clear mind.
When I first played Old World Blues in Fallout: New Vegas, I was stunned, it was a complete tonal shift that shocked me, and I came out of it with a big "huh?" After I played it again a few months later, I started thinking "Yeah, this is hilarious, it's funny." Likewise, once people stopped thinking "OMG, it's nice to have Liara back" and "Ooh, Tela Vasir fighting is fun", they could stop and say: "Hey, wait a sec, she's got my charred burned armor as a trophy. Cree-py" and "Hey, the third party member doesn't talk at all, despite it being Garrus or Tali. What gives?"
More to the point, people are still complaining about it now, and, like it or not, the complaints exist and have merit. Instead of making the argument that "Oh, they're just haters who are obsessed", accept that Liara was forced as a bestie, that she got far too much screen time to justify her flaws, and move on.