The obvious reason is to impress. There's always a part of a 'man' that yearns to be known for nice things, not the ugly ones which are most times locked away in the closet. I feel most times that people who blow their own trumpets probably have something to hide.
Yes no one is a saint, I'm not either and there are things I have done or not done in the past which have had negative impacts but I believe I'm still a work in progress. I have forgiven myself and moved on, letting those past mistakes help shape a better version of 'me'.
I agree, nothing more to add here. Thanks for your comment.