“happy” isn’t a noun, so no one would try to make it plural.

“Software” is a noun, but the plural version is often the same, i.e. “installed a lot of software.”

But since I was discussing “multiple different” instances of software, it made sense to treat each one as a discrete “software,” thus I used “softwares” to communicate “multiple different discrete instances of software.”

Just like how “people” is plural for “persons” but “peoples” means “multiple groups of people.”