Not sure if this question was meant to be taken as a joke or taken seriously -
If as a joke -
1) to help keep the economy going
2) to satisfy some "need"
If meant seriously - a lot of fabrics seem to have "short runs" - meaning that after whatever the manufacturer printed is sold out, then there will be no more available. If I think something is "gotta have it" - it is highly likely that someone else is also thinking that.
As far as buying coordinating fabrics - how much of each? - probably get the most of the focus fabric - one can sometimes "make do" for some of the coordinating fabrics.