Break ups are messy and a lot of feelings are hurt (this is assuming the break up was not due to violence or bullying).
Many people underestimate the feelings of the person that did the breaking up but whether they know it or not, that person also have questions such as "what could I have done differently so I did not have to break it off?" "How did it come to this?" "Am I an awful person for breaking it off?".
When a person breaks up with another, they also feel hurt. Yes, I agree that the person who was broken up with goes through a lot of emotions, but remember, the person who made that mature decision is also constantly questioning themselves. For people who hate hurting others, it makes them feel like the worst person in the world and even question if they should allow themselves to date again.
So remember this if you are ever broken up with: It is not like the person who broke up with you is saying "good riddance" (unless the reason for breaking up was because you were a jerk, controlling, hurtful, verbally or physically abusive). But even then, the break-uppers still feel that guilt.