In the modern era, encryption and decryption really is more of a computer thing. Back in the day, though, people had to figure out the patterns and algorithms by hand. Finding common words via such things as double letters were super helpful. However, encryptions were sneaky and would mess with spacing, having changing letters (a ‘w’ may be used to represent an ‘a’ in one location but may be a ‘h’ in the next), and etc. One thing that was cool about decryption, other than the math puzzle aspect of it, was its importance in such things as wars. If someone figured out an intercepted encrypted message, they had a huge advantage.