Question: Why can instant puddings be prepared quickly?
About the article "Pudding", section "Creamy puddings".

Candidate passages:
The second and newer type of pudding consists of sugar, milk, and a thickening agent such as cornstarch, gelatin, eggs, rice or tapioca to create a sweet, creamy dessert.
These puddings are made either by simmering on top of the stove in a saucepan or double boiler or by baking in an oven, often in a bain-marie.
These puddings are easily scorched on the fire, which is why a double boiler is often used; microwave ovens are also now often used to avoid this problem and to reduce stirring.
Creamy puddings are typically served chilled, but a few, such as zabaglione and rice pudding, may be served warm.
Instant puddings do not require boiling and can therefore be prepared more quickly.
This pudding terminology is common in North America and some European countries such as the Netherlands, whilst in Britain egg-thickened puddings are considered custards and starch-thickened puddings called blancmange.
Instant coffee, also called soluble coffee and coffee powder, is a beverage derived from brewed coffee beans.
Instant coffee is commercially prepared by either freeze-drying or spray drying, after which it can be rehydrated.
Instant coffee in a concentrated liquid form is also manufactured.
Examples of popular instant coffee brands are Extra, Folgers, Maxwell House, Nescafé and Starbucks VIA.
Advantages of instant coffee include speed of preparation (instant coffee dissolves instantly in hot water), lower shipping weight and volume than beans or ground coffee (to prepare the same amount of beverage), and long shelf life — though instant coffee can spoil if not kept dry. 
Variant forms of puddings made with breadcrumbs boiled with milk can be found dating back to the seventeenth century.
"The Closet Opened" was posthumously published in 1699 by a servant and his son and in it Sir Kenelm Digby talks of many puddings including one that involves soaking bread in milk.
There was a whole variety of puddings that could be made using the remains of some bread and some warm milk.
A "Monmouth Pudding" is said to consist of layers of meringue, jam or seasonal fruit and bread soaked in milk, whilst "Manchester Pudding" is similar but contains egg yolks (but some have speculated that this name was just a synonym for the "Queen of Puddings").
Typical recipes for modern Queen of Puddings can be found in many post-war British cookbooks, such as those of Marguerite Patten, Delia Smith and Jane Grigson. 
Quaker Instant Oatmeal comes in 1.5 oz (43 g) single-serving packets and is usually flavored.
Flavorings include cinnamon and apple, honey, and other "sweet" styles.
The oatmeal is prepared by mixing with boiling water and stirring, hence being referred to as "instant"; once mixed, the oatmeal is ready within a minute.
It can also be prepared by adding up to 2/3 cup of water and microwaving for 30-60 seconds.
Milk may also be used. 
In the United Kingdom and most Commonwealth countries, "pudding" can be used to describe both sweet and savory dishes.
However, unless qualified, the term in everyday usage typically denotes a dessert; in the UK, "pudding" is used as synonym for a dessert course.
Dessert puddings are rich, fairly homogeneous starch- or dairy-based desserts such as rice pudding, steamed cake mixtures such as Treacle sponge pudding with or without the addition of ingredients such as dried fruits such as Christmas pudding.
Savory dishes include things such as Yorkshire pudding, black pudding, suet pudding and steak and kidney pudding.
In the United States and Canada, "pudding" characteristically denotes a sweet milk-based dessert similar in consistency to egg-based custards, instant custards or a mousse, often commercially set using gelatin or similar collagen agent such as the Jello brand line of products.
In Commonwealth countries these puddings are called custards (often shortened to curd) if they are egg-thickened, blancmange if starch-thickened, and jelly if gelatin based.
Pudding may also refer to other dishes such as bread and rice pudding, although typically these names derive from the origin as British dishes.