Because Danishes are mechanically modified; namely, by the cooking-related skill. If it should ever happen that you have to bake a pastry, in a situation where the quality of your cooking counts, then you'll need to make a check against that skill to see how good your pastry is. If you don't have that skill, then you'll have to explain how it is that this superior baker doesn't know how to, uh, bake.
It is true that there is no "quality of pastry based on Craft (Baking) skill check" chart anywhere in the Player's Handbook. However, from the SRD:
So in this situation, where you want to make a pastry, the DM would need to figure out how much such a pastry was worth, how complex it was to make, and assign a DC and time-to-create on that basis. It's not just a flavor element; it has potential to affect the campaign storyline, whether you're using your skills to convince the trolls not to eat you ("I cook better than I cook," to use Bilbo's phrase), to get yourself a job in the kitchen of the Evil Overlord so you can spy out the castle, or to impress the gourmand king and earn a reward.The basic function of the Craft skill, however, is to allow you to make an item of the appropriate type. The DC depends on the complexity of the item to be created. The DC, your check results, and the price of the item determine how long it takes to make a particular item. The item’s finished price also determines the cost of raw materials.