I think it's because they do a bunch of GPA calculations for the school. Once they verified my GPA, it showed up in a bunch of new ways - GPA per year, per major, per upper-level courses, etc. By standardizing it, they save each individual school a LOT of time going through your transcript themselves. It may take 4 weeks on their end, but it means every individual place you apply doesn't have to go through 2,000 transcripts - which might take them eight, nine, ten weeks. SOPHAS has a system and the staff to deal with an influx of transcripts, but individual schools do not. It speeds up the process in the long run. Every person who applies is on a different credit system, different quarter/semester/trimester system, but SOPHAS standardizes that to make it easier to compare applicants.
That being said, SOPHAS often made me want to pull my hair out.