It's pandering, specifically to a small group of loud autists who don't care about characterization or plot. They just want a cute lesbian pairing to self-insert/project on.
Ignoring the comic Harley and Ivy, who by the way are currently not friends, this show and its narrative has done piss poor development to justify this relationship. I mean sure, they're friends, but beyond that we've seen ZERO romantic chemistry or hints they feel about each other in that way. Of course if you bring this point up to the shippers, they will go rabid and make every excuse in the book to justify it because they themselves don't understand real human interaction, hence why they're so possessive/defensive over the ship. A competent writer would have laid some groundwork, something like Harley or Ivy expressing curiosity in the same sex or questioning their feelings for their friend. We get none of that. All we get is one or two touching moments between friends either making up or enjoying a moment that we the audience are supposed to buy as "romance".
Shifting gears back to comic Harley and Ivy, I don't really care for the ship because its counterproductive for both characters. On Harley's side it makes her character weaker because it waters it down to relying on a love interest to be relevant which goes against her arc with The Joker, whereas with Ivy it wants the reader to forget years of her own characterization/disdain for humanity, essentially becoming a side character for Harley not allowed to do anything anymore.
So in short the pairing is shit in either universe, at least in terms of execution