Why is portal 2 on xbox one but half life 2 and tf2 aren't?

[Prussia]

Always felt weird that they're separated by console versions, like half life 2 on the older xbox, and tf2 on xbox 360 but then we only have portal 2 on xbox one

[Mλrtin2H]

The Orange Box is available for the Xbox One, that includes HL2, the episodes, TF2, and Portal 1. I did some googling, and it seems like you can't buy it digitally anymore for some reason, but you could get the original 360 disc version on ebay or something, that should still work.