The only satisfactory excuses I've ever heard are that gamma correction used to be quite expensive, and that computers can't measure the gamma of the screen they're attached to. But even the second of those ought to have been fixable with PnP. Beyond that, all I can think is that if someone is used to a value, they'll get confused if it changes.

So yes, it basically sucks in that printers have a gamma of 1, so a monitor with anything other than that makes things tricky. And woe betide if your monitor has different gamma values for different phosphor colours. But since most graphics setups can't apply a variable correction, we're basically stuck with it.