WARNING: There is a link to /r/saltierthancrait. If you despise that sub, I don’t recommend reading it.
TLJ give no motive why Rey’s parents left her on Jakku.
That’s the point. When Rey admits her parents were nobody, it meant they had no good, actual reason to abandon her, it meant they did this all for nothing, that they didn’t care about nor love Rey, they didn’t give a shit about her. It meant that, to her parents, she is worthless. Even if you cut out Kylo Ren’s following lines, it still has the same meaning. I heavily recommend you re-read the section of her TLJ arc in my actual post itself, to understand what I’m saying.
It’s even framed that way in TLJ. Why else is she not affected by the truth by the time we meet her at Crait? Because she’s clearly moved on from her parents and accepted that they did throw her away like garbage, that they did think she was worthless, and now she’s relying on the Resistance for validation.