Significance of learning 32 bit exploitation

I’m thinking of taking EXP 301 (Windows User Mode Exploit Development) exam. And I did some research on this exam; I came around many articles which criticised the exam material for only covering 32 bit (x86 Windows Exploits). So I want to know what is the significance of learning 32 bit exploitation.
Is this a pre-requisite to learn 64 bit exploitation?
Wouldn’t it be better to learn about exploits on 64 bit system considering almost every system is 64 bit nowadays?

Source: Windows Questions