Many people wanting to try a new(er) version of a software but who are concerned about it "breaking" their customized setups/configurations using their older versions of the same software, like the current ability to have the two versions exist side by side. This lets us decide if/when we're ready to switch to the new software version completely by uninstalling the old version. Experimentation or issues with the new software can be safely done without risk to the "known good" setup of the older version.
While some software like the ones you mention (most being freeware) use the install/overwrite model, there is the risk that the new version would not work as desired for the person who did the upgrade. In that situation, the new version would have to be uninstalled then the old version be reinstalled. Some software upgrades could also change the user's data files / database fields etc. in ways that are NOT compatible with the previous version of the reinstalled software which could require restoring a recent user created backup. If the user didn't have a recent backup, it could be a worst case scenario of unrecoverable user data loss. This scenario is fortunately much less common than in past but...
I have spent a considerable amount of time on my media collection/library over the years so I far prefer the "you can safely try the new version side by side with the old one then uninstall the version that you like least" approach currently used by JRiver. Based on your recent posts with questions/concerns about upgrading from MC28 to MC32 with your VSTs, I think that the risks inherent in the other approach would be something that you'd prefer to avoid.
