I agree most the mainstream posting is done including pars. However (without actually looking) I would wager to believe there are some cases where par files are not included. Also, if a person used the "delete par2 files" option, and the original files were saved (which, I do), it WOULD be necessary to use these sfv files in the future... if there was ever a problem.
Obviously ... these are the exceptions to the rule, but so is complaining about 1MB of sfv files after downloading 1.5TB of data. They really are miniscule, EVEN IF they were truly redundant.
I doubt it would take much to implement (as the functionality is already there) ... but I believe people who chose to use the option would end up with problems at some point.