I've never used the site you mentioned but I think the idea of being able to own digital works with the help of the blockchain is very important. When you buy digital things on most web stores, it's actually just like leasing the products. If the site ever decides to shut down the site, you lose access to everything you "own" on that site.

If Steam, for example, ever went out of business, millions of people would lose access to all of their games that they've bought there. That thought is deeply concerning to me.

There is a way for certain games that you buy VIA Steam to be both on GOG and Steam, but it's very few. There are actually a few games that I've mistakenly bought on both Steam and GOG because they were on sale and I forgot that I had bought them. What would be nicer is if they just interfaced with a blockchain and I could download the games I bought from either, if they have them.