Consideration indicates mutual assent to the same terms and conditions. It also has another purpose. It tells us that the parties were serious in intending to contract.
However, consideration has also been used to invalidate what might otherwise be acceptable situations in which the law might enforce. For example, if I agree with my nephew to give him a car to go to college with, and later refuse. There is no consideration to this transaction, and so a necessary element of an enforceable contract does not exist. However, is there any good reason why the law would not enforce my promise?