More complexity, more chance of problems.
For example, my dad used to use Androids. Without fail, he would get malware on them, he simply could not resist bypassing the security prompt to click on something he wanted to click on. Or maybe he does not understand English, or the concept of malware enough to properly heed the security warning pop up.
With iPhone, it’s not possible, so there is no worry, and no malware. Same with the hardware changes. People like my dad, or my wife, or even me who have very little interest in technology simply want to trust their device. And this device is literally the key to their life, their financials, their personal data.
All I know is my life has been made much easier by slinging Apple devices at people in my family that they simply do not have a way to mess up.