They are not measurable - in other words there is no metric that can be derived from the supposed effectiveness of the campaign to get the ROI figures. A standard advert banner may raise awareness but you never know what the engagement is.

Standing banners cannot necessarily cover a large area, it cannot reach a large audience.

They also do not have great memorizing value.

They may usually go unnoticed due to it's size.

They are difficult to alter.

They have a short life.

Expense / Catchment / Singular promotion potential.

They require space, they aren't easy to change, they can blow over.