Professional artists are more likely to be proficient with the commercial apps. Said pipeline might have room for simplification or optimization. There could be

Professional artists are more likely to be proficient with the commercial apps. Said pipeline might have room for simplification or optimization. There could be a lot of reasons. In Factorio's case, they've ended up remaking a lot of their art assets to a higher standard of quality, so that would have been as good a time as any if they had wanted to switch.