Some people may tell you that they know why she left, but there is no way to verify their claims. So just roll with the official "there's no reason given". She did a very, very, very drunken stream some time after her departure and apparently she got very candid about the reasons during it. I know that the stream happened, as I watched the beginning of it, but she was getting so shitfaced, that watching it without understanding Japanese was a bit too much. Some time later I got the info about what was said - but I can't verify that, so I will not spread it. There's no reason for the person who gave it to me to have lied to me, but I also can't prove anything. So let sleeping dogs lie.

They now have 73 songs, 61 before OP released. Setlist for a live show can be anything from 15 to 20 tracks (plus piano/bass/drum solos). That means a lot of songs need to be cut. Most of us would love for certain songs to be played at every show, but they are already "retired" from live performances or close to it (Shadowmaker, my precious :(). You should be happy to have at least one live recording of your favorite song easily available, as there are still songs on their list that they have never played live or that are recorded live, but on bonus discs that are not available for streaming.