Hi. I'am a beginner and studying a given file. I wonder what the point is having a mesh parent related others? just for convenience so that you can move all of them easily? why don't they manage via collection? is there any beneficial reason or situation for doing this for particular purpose? I thought this feature is only used for rigging.
Parenting provides an important convenience in organizing assemblies of objects - as mentioned in the commentary to your question.
But I guess the most important distinction between joining or grouping objects and parenting them is that, as far as transforms are concerned, the parent-child relationship is one-way. Children inherit the transformations of their parent - but a parent does not inherit the transformations of its children. This is vital to animation and rigging.
Consider a fairly simple animation of, say, the Earth orbiting the Sun, and the Moon orbiting the Earth (even without rotating at different speeds on their own axes) .. try it without parenting, and you'd soon be convinced of the need for it. There would be a lot of maths to do :)