It has much to do with rural demographics. Many areas in the Midwest are losing population. Young people move away. Older folks pass away. Neither group gets replaced.
Congregations dwindle, and churches, their ranks thinned, disperse or consolidate.
Not all ecclesiastical salvage goes into private homes. We had a huge altar that we sold to a church in Canada. And new churches that are being constructed often come to us looking for stained glass. First of all, they're just glad the things aren't being destroyed, but to sell to another church gives the objects another life within a religious context. But many ecclesiastical objects wind up in private homes.