Because customers pay for it, there is enough money to invest to improve its quality by buying the necessary devices and tools to keep channels with the least percentage of buffering any time lagging. Premium IPTV service is first, well-managed, cared for, and hence more reliable.
And IPTV industry, if we are allowed to call it so, is no exception. In most cases, paid services are greater than free services, no matter what domain or industry we talk about.