This question bothered me a few years ago when I pulled up my mother's phone, only to find out that XPERIA's beautiful home screen had been destroyed by the wearer's custom boot animation. I had also found a lot of bloatware that could only be disabled, delayed updates, etc. (we all know what happens, there is no reason to go into depth).
I searched the internet for an answer to this question, but without success. Can someone answer that to me:
Why do operators install their version of the operating system on mobile phones and not?
leave the original firmware untouched by the manufacturer?
I do not think it makes any difference to carriers compared to users who have a worse experience.
(Also let me know if it is a duplicate.)