I know that very well, but in this case it is not possible to use for a very simple reason - it is not me who "creates" the website.
What you are talking about is 100% responsive design, something that uses the concept of segments, something like Bootstrap. Now, the problem is that you can easily do that when you know what you are working with. In my template, you as a webmaster have complete freedom over how many columns you put on your homepage, which blocks you use, how wide you make the columns, how many there will be etc etc.
That is all great, but obviously it also has its downsides. Given I do not have one predefined layout, I have no way of doing what you suggested because I have no clue what each user puts on their homepage, how wide they make the columns, how many... so I cant adjust it simply because I have no clue what I am trying to adjust if you see what I mean.
So I created the "mobile version" and it is recommended to only use one column or two columns there. What I can do and I did is make further modifications to the mobile section to make it work better on smaller screens - there is the hamburger menu, there is different font size scaling etc.
It is a compromise:
1) make one static homepage layout for everyone, fully responsive
2) give total freedom for the layout to the webmaster, but no possibility of using one page for both mobile and desktops
Vast majority of people prefer the latter option, so I used that.