Easy, hotmail gives you a free account, how do they make money giving away free accounts?
1. from the people that are stupid enough to buy their paid accounts.
2. By selling your email address to tons and tons of spam companies.
I am glad I use gmail, I only use hotmail to chat with my friends, and the only time I check my hotmail account is when I want to make sure it hasn't expired yet so I can still chat with my friends.