Everybody has their own style of work
It is logical to have this button, at least as an optional feature
I do not know, may be the reason is a very small drop-down button, that you got to search on the high DPI screen, and sometimes pressing preview button instead
And the shortcut isn't very handy
I have a big hand and compact laptop keyboard, but even for me to press Shift+Fn+F5 is hard even harder than to find a small arrow of the preview drop-down menu
Can't say that can't work without a separated debug button, but in the C2 it was realized much more intuitive