Most of the hosting providers use virtual hosting, it means that there are multiple sites/domains on a single IP.

There are many resellers on the server and the best option is to set a dedicated ip address for every reseller. It's useful for both provider and reseller. Also providers may offer static ip addresses for SSL purposes (every SSL site requires a dedicated IP, so providers can't host multiple ssl sites on the same ip) or private name servers. See details for their reseller plans, I'm sure you will see something else regarding the IPs.