Could have a million reasons ...
1) To make up for the release of her original solo being delayed for a year if not longer?
2) To prep the general public for a possible Solosé in the near future when BP is on another hiatus?
3) To provoke conversations about their motives and generating buzz? (Obviously works in this fandom)
4) Or maybe the song just fit sonically and narratively into the Born Pink universe?
"Hard to love" has me humming lightheartedly to a song that deals with trust and commitment issues. That's gold.