When you are drilling new keys but you absolutely do not want to look at the layout map that shows the keys you are supposed to know already.
For me it doesn’t matter much. Since I have a contoured keyboard nearly all alpha keys are easy to reach with my hand on the palm rest (not hovering). But I’d rather have h on the home row as well, since it reduces finger movement for frequent bigrams like th. I have backspace on one of my thumb keys, but I don’t use it frequently, to it’d be more optimal to put a letter like e there, so that h can move to the home row. So even though I use Colemak-DH, I am experimenting a bit with other layouts like Maltron since I don’t believe Colemak it necessary among the best layouts, it just gained quite a lot of popularity. Well and it’s fun to rewire parts of your brain :).
It’s a bit of a shame that layouts are high effort. Given a large enough budget, you can try multiple ergo keyboards. But the cost of learning a layout is so high that people experiment only little with it (if at all), so people continue to use QWERTY or if they learn something else it would be Colemak now or Dvorak 20 years ago. Of course Colemak and Dvorak are large improvements over QWERTY, but they may also be local optima.
