The answer to this question essentially takes up much of Chapter 9 of Guns, Germs, and Steel. In that chapter, Diamond explains why most large mammals are not suitable for domestication. To get the detailed answer, start reading at the bottom of p. 168, where Diamond asks why the “other 134 species” were not domesticated. He then goes on to answer the question, claiming that “we can recognize at least six groups of reasons for failed domestication.” Here are the groups.
Diamond says that some animals’ diets are not suitable. He mentions carnivores (because it takes too much biomass to feed the animals they eat) as well as finicky herbivores like koalas.
Growth rate. In order to be worth domesticating, an animal has to grow pretty quickly. You don’t want to have to feed an animal for years before you can get any work from it. This is one reason why people never domesticated elephants or gorillas.
Problems of captive breeding. Some animals do not breed well in captivity. You can’t domesticate an animal if it won’t reproduce.
Nasty disposition. Some animals are simply too mean to domesticate. Diamond mentions grizzly bears, but he also discusses how zebras have very bad tempers and therefore cannot be domesticated like horses.
Tendency to panic. You can’t domesticate an animal if it tends to panic easily. Imagine if cattle stampeded often. It would be too hard to keep them penned up and you would not be able to domesticate them well.
Social structure. Diamond says animals that can be domesticated almost always A) live in herds, B) have a hierarchical social order and C) have territories that overlap the territories of other herds. These characteristics make domesticated animals more tolerant of other individuals and easier to control. Animals without these characteristics would be much harder to handle.
Because animals have to have all of these characteristics to be domesticable, the vast majority of large mammal species have not been domesticated.