when you are in the frontend and you are editing your profile. The form is what I want to be able to re-arrange. The layout is kinda bad, I mean this is 2019 and we are using straight vertical forms? Gender is too wide and birthday is short so why not put them on the same line?

Forms are designed using mobile first approach, so first we tested on mobiles. Then we can change something for desktops. 

Another reason is that forms are buildable via Forms Builder and we can't make custom positioning of elements since it could be changed at any time, so more simple layout is used which will not break form when form is changed via Forms Builder.