I replace my computers before I ever feel a need to upgrade them. Computers are fast and performant for a long time now (4+ years, especially for non-professional use).
And as someone who works with computers all day long, I never ever want to open one up unless I build one from scratch and want a personal project.
Once upon a time I'd use the same monitor for several generations of desktop. But lately monitors feel like they're advancing more quickly and computers more slowly such that I end up replacing them after about ten years.
I personally appreciate not having to do both at the same time, but at least for me it has reduced that particular criticism against all-in-ones.
And as someone who works with computers all day long, I never ever want to open one up unless I build one from scratch and want a personal project.