Out of interest what padding are you referring to?

I would argue the main areas are pretty much covered.

  • Selection of inbuilt themes
  • Addition of theme via plugin (like macOS theme)
  • Addition of themes via CSS
  • UI modification for advanced users by CSS.

I wouldn't say that eliminating UI padding by modifying the application CSS is a standard user practice, many apps don't offer anywhere near that level of granularity outside of advanced config such as css.