We use decimals every day while dealing with money, weight, length, etc. Decimal numbers are used in situations where more precision is required than the whole numbers can provide. For example, when we calculate our weight on the weighing machine, we do not always find the weight equal to a whole number on the scale.
The main advantage of the binary coded decimal is that it allows easy conversion between decimal (base-10) and binary (base-2) forms.
The choice of hexadecimal representation is taken because of human readability and ease of conversion. This also works the other way round so it is much easier for big binary numbers (that appear in memory addresses) to convert them into hex and manipulate them with this representation.