Why i need extract not one needed port, but full catalog never needed ports?

[Виктор Кутенков]

Hello.
I'm try find minimum size OS for server / and as desktop. 
For server I try use freebsd+nginx+python.
For desktop freebsd+i3.
The clear freebsd size is ~1Gb. - it is the minimum OS that i found - It is my favorite now.
I like work with ports. But why i need dowload and extract ~1Gb empty folders? Is it posible to use next algoritm, for example:
Do not make portsnap fetch extract
immediately after installing the system make:
# /usr/ports/x11/xorg make install clean
1. freebsd check the directory /usr/ports/x11/xorg
>> it is empty
2. freebsd check the internet for search "/usr/ports/x11/xorg"
>> it is found "data"
3. freebsd dowload and compile data from internet.
Why it must make portsnap extract ALL never needed empty folders to system before? Is it posible make in future - search and extract from internet only one needed port? Like # pkg install xorg

This thought haunts from the very beginning of acquaintance with bsd. Sorry for my illiteracy in IT

Viktor