Should `legend.key` inherit from `panel.background`?

[teunbrand]

One thing I often forget when I change the panel background is to also change the legend key accordingly.
I'd like to propose that the following code:

library(ggplot2)

ggplot(mpg, aes(displ, hwy)) +
  geom_point(aes(shape = factor(cyl))) +
  theme(
    panel.background = element_rect(fill = "cornsilk")
  )

Would produce the same plot as this:

ggplot(mpg, aes(displ, hwy)) +
  geom_point(aes(shape = factor(cyl))) +
  theme(
    panel.background = element_rect(fill = "cornsilk"),
    legend.key = element_rect(fill = "cornsilk")
  )

^{Created on 2023-11-29 with reprex v2.0.2}

It would be a convenience if the legend key inherited from the panel background, to keep these in sync automatically.
To make this work as intended, the themes should probably omit the legend key definitions. These currently have a slightly different fill ("grey95") than the background ("grey92"), but I think the difference would be barely noticible to a human eye.