Why do so many tablets contain lactose?

[PaperPanama]

I've just started taking Montelucast for my asthma again. I know what it will do to my guts! Ok, better the squits than being unable to breathe, but why? Why do so many tablets contain lactose, when it is such a common intolerance?

To piss off those of us with lactose intolerance.

It's not piss that's the problem! I've got a review next week, I'll ask for a lactose-free formulation.

I'm guessing lactose is cheaper than the alternatives.

The replacement is mannitol which causes other side effects
I can't do either and artificial sweetness are in loads of stuff and they cause problems too

Why not microcrystalline cellulose? It's in other tablets.

it's a binder that allows for tablets (or those granules in caplets) being pressed together.

a binder needs to allow the active ingredient to be evenly distributed and not react/spoil the medicine.
lactose particles are very fine, much smaller than, for example, cellulose that is often used for vitamins/supplements.

Im now down to one brand of levothyroxine, solely due the additives and fillers