bit-wise. You manipulate bits (yes, those little 1's and 0's) as such.
What is hex good for? What is the decimal system god for?
Think about this: digital computers very often use the binary number system (base 2). In the hexadecimal system (base 16 = 2^4) a digit like A (= 10 in base 10) takes exactly 4 bits so the conversion from hex->bin and bin->hex is very straight forward. Where do you need this? When you have to convert different number encodings or text to/from base64 encoding or...