I didn't assume anything; I've known Blockland since late 2008, a few days before roblox.
I am only asking why isn't it around, it would make building easier and reduce part count.
It's because blockland simply doesn't support that.
Blockland works by setting datablocks, which are basically definitions of an object, so the client knows what to work with.
The server can tell the client, "Put one red 1x1 at 1,2,2!" and the game will know what it means.
Now, that's the .blb (BlockLandBrick) format. if you were using the .dts format (dirty twisted sickos (just kidding) ) then you could do what you're asking. However, .dts requires more processing power to render, which is why roblox is so lousy.