A combination of all those cited reasons, clearly. With the exception of the band members option, though, with whom I have no issues with. It is what it is, and they do a very good job 97% of the time. I doubt that the Average Morrissey Fan gives two tosses about who is in Morrissey's band, honestly. What they do care about is getting their money's worth when they shell out big dollars/pounds/euros/etc. to see a Morrissey show. Even the most diehard supporters of 2014-2018 Morrissey must agree that often (though not always - a couple of the London shows last tour looked quite nice) the shows can be a little choppy/anti-climactic/heavy-handed/poorly sequenced/generally same-feeling because of Morrissey's choice of songs.
And if you disagree, then you must not have ever seen a Morrissey show prior to 2014.
And before someone says it, I'm not advocating for a Greatest Hits-type setlist. But there are so many great songs that sit on the shelf for years and years while he continues to pummel us with much of the same-old, same-old tour-after-tour. Morrissey's idea of giving the audience a special treat is to dust off "All You Need is Me" or "Don't Make Fun of Daddy's Voice."