Because most people out there rather find xLib and MirageOS than DoorsCS.

So yeah, i did play a bit around wiht the DCS GUI lib, and it is pretty awesome

i know i said this earlier but i can use dcs alongside zstart just fine
maybe you should change some of zstarts settings?

I know that, but it is not the problem. I just don't want to "waste" 49152 bytes for a GUI that I could (re)code in my programs for less than 1000 bytes. Moreover, using DoorsCS would prevent my friends from using my program due to the lack of memory (they don't have the new 83+.fr USB).

The GUI can be pretty handy if you happen to use xLIB and Celtic too, as it will shrink down your program size while not forcing you to install Celtic, plus you can then run ASM programs. But yeah, this can be problematic for those who don't play games or only want to use one program, especially if they have the older 83+ like we have in North America.

Also, over here a lot of people prefer to create their own GUIs anyway.

I don't see where I stated that I would recode all the functions that the GUI offers in 1000 bytes. Of course my program would be limited to the functions I need. But I don't even think that would be a problem because I personally think (and it seems that aeTIos thinks that too) that the mouse is beautiful but annoying. And with a lot of simplifications (like no windows on top of others (so no complicated stack system), which "never" happens in a program anyway or you only have 2 of them and you can find a workaround (like a simple RecallPic)), yeah, I can have my GUI (and once again, not the real GUI) in less than 1000 bytes.

It is the same reason why I use zStart, not because it does all what DoorsCS do, just that it does what I need in less space (and does it faster), and no more.

Many of the GUI functions DCS provides are quite awesome indeed - but like Hayleia pointed out, you can simply code those yourself depending on your needs. And I still don't like to use any shell at all - imho I think that a mouse/cursor system and a calc don't fit together. I don't see any advantage if having a mousecursor when you don't have a mouse or a touchpad attached (unless you own Kerm's ultimate calc). It is rather annoying and slow.
Other shells still have to be launched as an app to work - and when you run them on power on, you need to exit them when you want to do some calculations. I might be a fusspot but every button click you can save is worth saving it. So the only shell to fulfill these needs is zStart:: you can still use the good old program menu and run your asm programs without fiddling around in the catalog - and it provides other developers features I can't imagine things without.
I know we're talking about two different things right here - but DCS and its GUI belong together imo and needing multiple apps (a shell for executing and organizing - and a library for your graphics stuff) simply take a lot of your valuable memory.
On the other hand, since Axe became that popular, the number of TI-Basic programmers dropped and therefore TI-Basic libs cease with them.

Actually in DCS's defense, you can also run programs from the home screen too.

True - I don't want to do DCS down - it's only my opinion. Why would someone put a 49k app (compared to zStart's 16k) on his calc when he doesn't come close to needing all the functionality. The idea of having a single app that combines the functionality of many other libs and shells - and adding more, like a GUI - is great as such, but I simply find memory more valuable when I think of all the stuff I don't need. Therefore I simply don't have DCS on my calc and thus I don't program anything that uses its libraries.
There might be people out there for who DSC is just the right thing, but I don't belong to those.