I talked to someone who created a startup in this space, specifically a two sided network for a type of construction material. She said it's all hyperlocal (no one is ordering from a supplier 3 hours away), most orders and planning are done on the fly and over the phone, and there are lots of local quirks that frustrate attempts to provide a one-size-fits-all solution.

Another example: I recently learned from someone who specializes in foundations in a rural area that he only has two options for ordering large volumes of concrete: a quarry 5 miles away, or a quarry 15 miles away. Any further, and there is a risk of the concrete drying out before it arrives at the site. He prefers the nearest quarry, even though it's smaller, because the owner hasn't yet moved to computer-controlled mixing and errs on the side of caution when creating a new batch, which leads to a better grade of concrete than its supposed rating.

ETA: concrete, not cement per @gtfoutttt