Popular streamer and content creator, Adin Ross, recently revealed his plans for building an crypto economy-based GTA 6 server. He suggested that this would be a server where players could earn in-game currency for performing tasks, and then cash that out in real-life. Many fans found the idea intriguing; however, many were quick to suggest that it very likely would not sit well with Rockstar Games.
Rockstar is yet to comment on Adin Ross' server plans as of this writing. That said, there seems to be a reason why the developer might not like Ross's GTA 6 server idea.
Note: This article is subjective and only reflects the writer's opinions and analysis.
Here's why Rockstar Games might not like Adin Ross' crypto-based GTA 6 server idea
During an episode of the FULL SEND PODCAST, Adin Ross shared plans to come up with a GTA 6 server running off a crypto coin. He wants to let players make money in-game through various activities on his server, and then cash those earnings out in real-life for a certain value of a crypto coin (on which he hasn't decided just yet).
Fans reacted to Adin Ross' GTA 6 server idea with intrigue, but with a lot of skepticism. Many of them believe that it would go against Rockstar Games' Terms of Service (ToS). Hence, the server would likely be taken down. As already stated, the developer hasn't commented on the matter. However, the Legal page on its official website seems to suggest that this server concept likely goes against the ToS.
Here's what Virtual Items section on the Legal page states about the sale/transfer of things like virtual currency for real money:
"Virtual Items have no monetary value, cannot be used outside of the Services, and may not be sold, transferred or redeemed for real money or items of value outside of the Services unless subject to separate, express written terms provided by Rockstar permitting such conduct."

This seems to be the reason why Rockstar Games might not like Adin Ross' GTA 6 server idea. Additionally, such an economy-based online ecosystem could prove problematic if attacked by hackers.
Nevertheless, it remains to be seen what eventually becomes of the popular streamer's proposed server. Grand Theft Auto 6 is currently set to launch during fall of 2025, but notably, only on PS5 and Xbox Series X/S, whereas RP servers (such as those of GTA 5) are limited to PC. So, we may have to wait for the upcoming title's potential PC port to see if Adin Ross is able to go through with his plans or not.
Also check: 5 possible ways GTA 6 could give metaverse-like experiences