To be fair, Foos' played Geelong because the city paid them to do it there instead of doing Melb.
As for why LP aren't as popular in Aus anymore, my read is that there's a cleanness to post-MTM LP that doesn't means it doesn't really vibe with Aussie's rock culture which is a bit rougher/scrappier/grungier (think The Chats, Amyl and the Sniffers, Violent Soho) while Foo Fighters still tap into that a bit and really ride off the populatiry of Wasting Light & everything that came before it. While LP miss that market, they also aren't clean enough to tap into our pop-rock market, and aren't consistently heavy enough to tap into our modern metalcore market - though with the amount of metalcore supports they're doing on this whole tour (not just Polaris in aus but a lot of their global supports) it seems as though that's the market they're trying to lean into.
I'm glad that I'll get to see them at home, but honestly shocked they're bothering to do Adelaide without doing a price drop. Ticket prices are so high that there wouldn't be many people who can afford the tickets but can't afford the trip across to Melbourne or Sydney, and because of all the above I don't know if there's a huge casual audience for LP (especially casual audience willing to pay the high ticket price)