Eh, because of the viewer's contrast sensitivity function scaling in linear space can give worse looking results. I'd say there are four reasons that processing is so often in a non-linear space:
1. Since our 'raw' formats are non-linear, processing in that space is what happens when you don't know otherwise.
2. It's much more computationally efficient to not convert into linear and back out again.
3. Given the low bitdepth of our image data, going in and out of linear space and doing even minimal processing can easily produce banding artifacts in smooth areas.
4. Due to the human CSF scaling in e.g. sRGB can give results that preserve the apparent structure in the image better, while a linear scale can look bad by comparison. sRGB levels also more correctly represent perceived levels, so thresholds based on sRGB ratios will work more consistently across brightness levels.
I'm sure plenty of people have seen internet comments about linear processing, went and implemented and found the results looked worse for reasons they didn't understand and abandoned it (and plenty of others who didn't notice it looked worse and crapped up their code without knowing it. :) )
1. Since our 'raw' formats are non-linear, processing in that space is what happens when you don't know otherwise.
2. It's much more computationally efficient to not convert into linear and back out again.
3. Given the low bitdepth of our image data, going in and out of linear space and doing even minimal processing can easily produce banding artifacts in smooth areas.
4. Due to the human CSF scaling in e.g. sRGB can give results that preserve the apparent structure in the image better, while a linear scale can look bad by comparison. sRGB levels also more correctly represent perceived levels, so thresholds based on sRGB ratios will work more consistently across brightness levels.
I'm sure plenty of people have seen internet comments about linear processing, went and implemented and found the results looked worse for reasons they didn't understand and abandoned it (and plenty of others who didn't notice it looked worse and crapped up their code without knowing it. :) )