Numerous source games that you could play on Mac before 64 bit was mandatory. Why can't Valve just update the binaries??
Valve seems to be making a pretty strong effort to distance itself from working with that engine where possible (though it's unclear if their lagging tentpole title Team Fortress 2 will get the Source 2 treatment)
It's possible that rebuilding these games for 64-bit Macs specifically would encounter an undesirable amount of bugs
Sure there are minor bugs like flashlight in HL2 not working correctly.
But IMO Valve just don't care about macOS to assign even one engineer to fix this and compile the new binaries.
Q1