Cloth mills rarely, if ever, work directly with individual consumers. They typically work with distributors or large customers. Less frequently, individual tailors may commission special designs and weaves just for their shop. The cloth is probably produced in a length of 20-30 meters and will likely go to several of the tailor's customers for their suits or jackets.
Taking the logic of customization even further, one can imagine a true one-for-one cloth commission from mill to consumer. We are getting closer to that reality - mill to tailor to consumer.
Cooper & Cooper is a bespoke tailor based in Huddersfield, the home of fine English textiles, and are now offering a single cut-length bespoke cloth commission individualized to the customer. They call this their Bespoke Cloth Designer.
I suspect it is just a matter of time before cloth mills find it worthwhile to go direct.