Wow, I have a 2012 Mazda3 and have the same problem, which only really surfaced during the pandemic when I stopped driving my car regularly. The dealer said it was just a normal level of drain (even though it would die in just 4 days of non-use) and I should get a trickle charger. Which I did, and is annoying, but is something that I can deal with. I’m not sure if I’m willing to disconnect my remote entry to see if this fixes it, but I’m glad others have seen similar behavior because it really bugs me that the mechanics would just shrug and not really diagnose why this was happening.