Moles are used because they are useful abstraction. When you want to get from reaction equation to actual real word having some fixed weight is useful. It becomes useful to have fixed relatively usable quantity to work with.

They are relatively decent size for actually weighing out things.

And honestly mapping number of elementary particles directly to grams is not unreasonable. Even if because physics of world are tad weird there is still possibility for some sanity checks.

They're not necessary, just a complicated way of doing what SI prefixes already do. Chemists don't notice this because they're intertwined with a whole network of conventions that would all have to be discarded at the same time. That's the legacy effect - it's too hard to untangle all at once.

Inches are a relatively decent size for measuring lengths too, but people manage without.