I just upgraded to PSE 2020 today and I'm curious what others do...do you keep the older versions on your computer OR do you delete them? I currently PSE 14 & 19 on my computer. I know having the old ones don't get in the way of the funcationality of the upgrade but I'm thinking I'd like to free up the space on my computer.
As John says, users sometimes keep older versions because they like to use features that no longer exist/have been changed in the newer version. The slideshow editor is a good example, but there are others.
Personally, I keep several versions on my computer so that I can help out folk with older versions on this forum.
One other point that is worth mentioning if you are concerned about saving space. Your older catalogs will not work with the current version of Elements. Hopefully, the old versions have been converted to the latest catalog. However, if you use several different catalogs for each version, you will need to convert any that were not converted automatically with the updated version. (Only the most recently used catalog will be updated when installing the latest version.) Once you have converted the older catalogs, these can also be deleted. Deleting the earlier programs will not delete the catalogs.