Why do the the authors of lobs girl and jeremiah's song use flashbacks

They use flashbacks "to inform all the more concerning a character".

Flashback is an intrusion of the sequential succession (starting at a film or artistic work) of an occasion of prior event. Flashbacks are intrusions that essayists do to embed past occasions, with a specific end goal to give foundation or setting to the present occasions of an account.

concern the charecter