Taking them out of the narrative and making them default skills often encourages player's to engage in lazy thinking. I challenge that this way: I have a gold pendant of particular value to me, personally. I ask such players how much it is worth and how they would know.
If the player truly doesn't know, they've just experienced what it is to live without appraisal. Most people know gold is valuable, and may even know what the required marks on gold and their meaning are, or be able to tell 24k from 14k and know what that means, but the weighing, assessing, even knowing the current value of gold, is more than just knowing that gold is valuable.
Having to acquire the skill (even if it is a bonus skill) gives it a place in the narrative. Your character went out and learned it, or was taught it, or otherwise knows why he knows the value of things.
Don't get me wrong. Having someone in the party with the ability to appraise makes the DM's job easier. You can roll when things are rare or odd but for the most part your party knows the value of things, and that means they can write down that they have a gold ring worth 25 gp, and you can stop keeping track of it.
This is why DMs get lazy with it, and say "you find an object of art worth 1000gp" instead of actually determining what the hell the characters found.
Here's the PHB description of Appraising:
Appraising: This proficiency is highly useful for thieves, as it allows characters to estimate the value and authenticity of antiques, art objects, jewelry, cut gemstones, or other crafted items they find (although the DM can exclude those items too exotic or rare to be well known). The character must have the item in hand to examine. A successful proficiency check (rolled by the DM) enables the character to estimate the value of the item to the nearest 100 or 1,000 gp and to identify fakes. On a failed check, the character cannot estimate a price at all. On a roll of 20, the character wildly misreads the value of the item, always to the detriment of the character.