What year is your i3? Earlier i3's have 3G data radios which would make the very large system software updates quite slow. Maybe recent i3's have 4G data radios which would make a wireless update much faster. However, with many different modules from different manufacturers being updated, apparently the updates can fail which is one reason why updates haven't been wireless in the past.
Tesla is able to provide wireless updates because it apparently writes most or maybe all of its software thus not depending on other manufacturers for software that might have compatibility problems with other software.