I have my moments and people that would likely disagree with that statement. It's more an issue of trust. Even the most trustworthy vampire can slip up and lose control-regretting it later. I prefer to have as much knowledge of each individual to know the difference in order to protect others from them.
It's about knowing the difference between yourself and other typical vampires that would arrive from your world. Why, if you you both attacked someone at once, I would handle them differently than you.