A really lame question, but . . .

Bob L, et. al
Why do we run AC to the filaments?
DC light bulbs like we used on boats last forever. AC bulbs in the house last maybe for a year or two.
Maybe there's a reason but I'd like to know it.Is it just the way the xformers are spun? Or does an extra rectifier complicate things?

I believe the extra cost to rectify the power to the tube heaters isn't justified in most cases with the exception of low level pre amp tubes such as phono pre amps.

Thanks, guys.
Was just curious. It's not usually that the heater craps out first, anyway.