What ? LBC is used on the platform to pay for the content, so yeah it does have a big role and there is a reason to buy.
There were also rumours(not really official though) that they will also accept all ERC20 tokens as payment, which will be converted to LBC in the background and drive it's price up.
So yeah, there is a lot of incentive for the price to go up!
But why use LBC when you could use dollar so makers and viewers won't have to think about best way to exchange their money and won't have to worry about their LBC price changing all the time. If anybody is going to make same decentralized videohosting but use dollars as their currency they will be one step ahead of LBRY from the start. And they will have much less loading time. And what is left of LBC if we remove the app? Looks like another scamcoin with premine.
It's like I will announce new coin (with premine, ofc) and say "Hey, it's pretty decent coin, because my new CS:GO-hats market will use it!". And then no one will ask me "Why?" but only praise my coin or just hate it.