You get lower prices and you can usually contract them.

Most big providers do not want to deal with clients bitching, money, complaints, refunds etc, they leave that to resellers. Some even in purpose advertise a high price online directly, so they can push clients to resellers.

There's a bit more to it, but sometimes the people involved with streaming don't want to be exposed; they have a lot invested on the line.

Also, maintaining a channel list is surprisingly a FULL TIME job for multiple staff. It's impossible to have them activating accounts and handling payments and keeping the feeds up, if you know what I mean.

Some providers don't deal with the public, and only deal with resellers, often in person (depending on the provider)

Thanks, I learnt something new. : )