Aside from saving gas or electricity, why cover the pot?
It retains heat &amp; steam pressure, so you achieve a simmer or even a boil with less power input &amp; less water loss.
Great for long-cook sauces. Not so good for starchy things which may boil over if you're not careful, or have the pan too full.
As with most things, familiarity with how your stove/pan/lid combination reacts to a slow simmer will determine how well this works for you. If your stove won't drop low enough, you'll burn things, or need to get a simmer ring to reduce the risk. If you tend top make things too wet, you need to adjust over time.
Making anything to an online recipe needs you to be fully aware of how your own kitchen responds to wet/dry/timings. I don't think I ever blindly follow a recipe, I modify to how it needs to turn out based on my own experience with similar ingredients/quantities.
If I guess wrong, then I'm reducing sauce in a flat panic over the last 10 mins… not a good feeling, but familiarity breeds content ;))
There was at one time folk wisdom that said, &quot;if it grows above ground, lid off, if it grows below ground, lid on&quot;… which I have pretty much ignored for most of my adult life.
Sure, potatoes boil best with the lid on, as you obviously retain the heat, but I'm pretty sure I've never boiled a leafy vegetable in 20 years, I steam them… incidentally using the 'spare' steam from my lid-on potatoes.