IThat means that, with only a skill of 20 in Restoration, a spell that you start the game with can heal you for 36 points per second (and cheaply!), which, if you didn't know, is incredible
Potions do heal instantly, means you can heal yourself in 0 seconds for unlimited HP as long as you have potions. 36 points per second is damage better bandit does with warhamer on you. One of the biggest advantage of potions is that it in fact cost no time to heal using them.
good self-made potions won't heal you for 36 points per drink until your Alchemy skill grows a lot higher than 20 (not to mention the fact that it's a chore just to get the ingredients, especially since some ingredients have better magnitudes than others).
I have no problem making potions which heal 60 HP on alchemy level 30. You just need to take perks. As for ingredients, they are plentiful, especially those you need for healing potions. They are literally everywhere.
It's essentially both free and infinite healing, as well as stamina regen with the proper perks (36 per second, again), and the spells get a whole lot stronger than that.
Problem with restoration is precisely that it is NOT instant, it takes time to heal while enemies are not sitting and waiting while you do so. And while it is free it is not infinite as it last only as long as your magicka does. If you are not playing mage character, you are not going to invest much in to magicka.
Edit: You can run out of potions. Remember that.
So you can with magicka.
Bye the way, does somebody know if companions use healing potions? Seems they do but I am not 100% sure.