LBRY was commenced a while back -- back when having your own coin was a cool thing to do. LBRY also uses non-standard transactions to purchase and build their URL tree. (LBRY allows you to acquire a named channel to host your content, similar to Youtube.)
In addition, Bitcoin at the time was plagued with performance concerns and high fees. If your vision is to serve and support content to millions per day, you want freedom to address the performance needs of the system.
I do think you could build a similar system on bitcoin; your wallet server could build the necessary indexes. You would need to do some interesting P2SH work to construct the channel hierarchy.
Producers would use this service over others to ensure that the content that they sell is not tampered with, not censored, not edited, not removed by someone else. They would use this service to be sure that their content got to the consumer in its pure form.
Consumers would use it for the same purpose: they use it to ensure that the content they are viewing is exactly what the producer intended. Consumers would also use the service to acquire content that has been wrongly-suppressed elsewhere.
One of the major things that blockchain solves is URL ownership. LBRY is trying to build a censorship resistant video service. The blockchain backbone allows public proofs of URL ownership and that specific content came from a specific URL -- it's like SSL without the central server or the chain of trust.
There is an element of URL ownership involved. It's not just a matter of finding and serving up video content; LBRY allows you to post that content at a specific URL. The ownership of that URL needs to be publicly verifiable.
In addition, Bitcoin at the time was plagued with performance concerns and high fees. If your vision is to serve and support content to millions per day, you want freedom to address the performance needs of the system.
I do think you could build a similar system on bitcoin; your wallet server could build the necessary indexes. You would need to do some interesting P2SH work to construct the channel hierarchy.