One of my n'bors is getting her house's air ducts cleaned now.

It seems to be that the dirt and dust that is loose gets blown into the
house every day with no need for a cleaning service (and before the
cleaning service can arrive), and the dirt and dust that isn't loose,
that requires a cleaning service, just sits there in the duct anyhow and
doesn't bother anyone.

When did cleaning air ducts become a desirable thing?