Following its policy to bring more PlayStation-exclusive titles to PC, Sony recently launched Uncharted: Legacy of Thieves Collection on PC, including Uncharted 4: A Thief's End and Uncharted: The Lost Legacy in a single bundle. However, the product has not become as popular as previous PlayStation launches on Steam so far.
As spotted by VGC, the peak concurrent Steam players for Uncharted: Legacy of Thieves Collection has been nearly 11,000 so far, which is far below the peak concurrent users submitted for Horizon: Zero Dawn (56,000+), Days Gone (27,000+), God of War (73,000+), and Marvel's Spider-Man Remastered (66,000+).
Regarding the fact that previous PlayStation titles hit their all-time peak concurrent players on their opening weekend, it is hard to imagine that Uncharted: Legacy of Thieves Collection could submit a new record, but it doesn't mean the game cannot turn into a commercial success in the long run. That being said, there are a number of reasons that contribute to this moderately poor performance.
Unlike previous PlayStation ports on PC that all had understandable, standalone stories, Uncharted 4's story is highly dependent on its previous iterations. Horizon: Zero Dawn, Marvel's Spider-Man Remastered, and Days Gone all were the first entries of their franchise. Even God of War (2018) had a story relatively independent of context as it was the beginning of a new saga for Kratos in a very different world.
Recently, Naughty Dog confirmed that it will probably never be able to bring the first three titles of Uncharted to PC, which is another reason why Uncharted 4 could not be as enjoyable an experience at the same level as previous PlayStation games for PC players, who may be stepping into the game with no knowledge of the characters, their past, and their relationships.
Other than that, the launch schedule for Uncharted: Legacy of Thieves Collection was crowded by other big titles such as Persona 5 Royal (PC version), Call of Duty Modern Warfare 2 Campaign Early Access, Gotham Knights, and even A Plague Tale: Requiem. Having all these new and anticipated titles launched in such a short period of time must have made it pretty difficult for a port from 2016 to become a bestseller on Steam.