Because I have played it and the game wasn't that great. The vanilla game is pretty much complete ass in combat which you will have to do eventually. The characters are subjective and whom I thought were annoying. It is true that there are multiple ways to solve some situations and I commend the game for that.
The vampire races are pretty interesting, but the implementation really is just the same with different character reactions (with the exception of the nosferatu which was fairly unique)
My biggest complaint of the game is that as a vampire, you feel weak as shit. I don't know if it is just the horrible implementation of powers or just asstastic combat, but I just don't feel like a vampire. The game also lies, because guns ARE the best weapons for both vampires and humans.
The vanilla is also ridiculously glitchy (quest bugging, npc disappearing ect.) and is really only playable with mods and the unofficial patch to fix the problem. The game is ok for me but the world really isn't that interesting. The hubs are small, the storyline really wasn't that interesting (ending is a hit or miss, I liked it), and overall it is a fairly short game.
Edit: Oh yes, the implementation of the powers was so clunky that I had to enable the console to manually bind the powers so they go off on key press