I suppose it's because he believes it will be more lucrative (more $$$, promotion, etc.) to sign with a big label. However, that's not really true today to begin with, not in 2023. And it's Morrissey - a legendary artist w/a deep catalog (from two careers) and at least X number of fans in the hundreds thousand globally. If he releases something very good - as per his 3 out of 4 ratio - most of those people will buy something. You can't let your good songwriters leave though, they need to remain. The two best we had just left (and they are really, really good). I sure hope they come back.
If he got this monkey off his back (desiring a big label) he could totally do it HIS way again - I hope he starts to see that. Also, these people who 'work' for him now, his nephew and the writer - they could be doing more proper work for him as employees of 'his label' or in charge of 'his promotion', etc. Something way beyond, yet more vital and concrete to his career, than what they are doing now.