Most Mac apps don’t have an uninstaller (or installer) you’re meant to just toss the app in the trash. The problem is this leaves in place your preferences files, any “application support” files it may have downloaded, maybe a cache, etc
That said, I’ve been migrating the same Library folder from Mac to Mac since around 2003 and have never used an app cleaner. It really isn’t an issue 99% of the time.