Open Sea is the largest market for NFTs, and at the height of the 2021 NFT boom it was earning billions of dollars a month in revenue from secondary market commissions.
The following factors enhance the popularity of Open Sea:
Many game projects launch with Open Sea as their primary market. Developing a blockchain game is difficult enough without the additional burden of building and running a marketplace on top of it. The existence of Open Sea and its adoption among NFT owners/traders makes it the natural choice for most NFT projects.
Open Sea gained prominence before the rise of blockchain gaming. As such, the Open Sea user experience is not well-suited to gaming use cases.
Gaming NFTs are different from other kinds of NFTs in that:
Open Sea largely relies on their users to update metadata on tokens if they want rapid updates, and do not even offer simple API access allowing anyone to update the metadata on a token.
It is (justifiably) unaware of the transferability status of particular tokens.
While users can filter tokens based on traits in their metadata, the fact that this metadata is so difficult to update on Open Sea means that the results of these filters are often stale.
Current marketplaces only allow for the purchase and sale of NFTs. They do not support any kind of lending functionality. This is a side-effect of these marketplaces having been built for art NFTs and profile pictures, and not for games.
Adding lending support to a general-purpose NFT marketplace would be very difficult given the number of different delegation models that blockchain games implement (or plan to implement). But for any particular game, it is absolutely essential for a marketplace to support lending of NFTs, because this is a very important use case for players themselves.