Beige is chosen when the planter should not be part of the conversation. Against sandstone, travertine, warm render or teak it reads as belonging to the building rather than placed against it, and it does that without the glare a bright white picks up in direct sun.
It has one practical advantage over white that is easy to miss. A pale surface absorbs less sun than a dark one, so the root zone runs cooler in an exposed position, and beige gives you that without showing every mark the way a bright white does. The satin sheen is part of this: it is easier to wipe clean than a flat matte and it does not hold a fingerprint the way a gloss does.
It is also the finish we reach for when a scheme has several materials already. A courtyard with brick, timber and stone in it does not usually need a fourth statement, and a beige planter lets the planting carry the interest instead.
