The reason why Apple decided to partner with Valve can be quite simple - Valve has some experience in VR and HMD. The company has released its first VR headset, The Valve Index, this April. Also, back in 2017, Valve worked with Apple to bring VR headset support to macOS back.
However, the new partnership will be focused mostly on AR than VR. According to Digitimes, Tim Cook believes that AR can make digital content become part of the user's world and will be as popular as smartphones with consumers. The new collaboration promoted Apple to recruit more engineers for graphic design, system interface and system architecture segments.
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