Why a damper isolation transformer?

[Findm-Keepm]

I understand that Damper tubes can develop a H-K short, and cause problems. But both Triad and Thordarson (26F70) made isolation transformers to isolate the damper filament from the rest of the chassis, and alleviate the H-K short issues.

But why use a transformer, when replacemnt of the tube would likely solve the problem without modification or added expense?

Perhaps some chassis were more prone, or the H-K short could cause many more problems? They were first made in the 50s, so probably not a color-TV specific problem....

Any ideas?