Moving gantry and table on the same axis - why not?

[suicidal_orange]

I'm a complete newbie to this and in the first stages of planning a build (yes, it's that vague for now) I've had the thought that if the gantry and table both moved on the same axis the usable length could be (nearly?) doubled without increasing the footprint of the machine for storage, while keeping the moving parts shorter should mean it's more rigid. I'm only thinking of around 350x200x50mm so short means short compared to most of the monsters in the build logs here!

I guess there's a reason no-one does this, would anyone care to explain it please? Or if people do do this and the design/idea has a name I can search on that's just as good