For good reason- - bonus abusers trying to cash out on 100% plus deposits.
As to playing at other's people homes, I generally just give the casino a heads up and it's fine ie if I visit my mom, she will play on her account, but we use my laptop because it's faster. And when she's in bed, I use my account to play. As long as the casino knows what's up, I've not found it a problem yet. A qucik pm, or asking beforehand goes a long way.
As to multiple accounts, same address, same deal - some casinos will allow 2 accounts, when you politely write them and ask and explain the 2 roomie relationship, or when partners want their own accounts. For example, the BF and I just use mine to save headaches, but over at 3Dice he has his own, because I don't want him logging in under my name and think I'm ignoring anyone pming me in chat. Form a relationship with the casino, get to know staff, and request nicely - they will work with real players they know deposit and arent in it for the bonuses alone.