Why is it considered a bad practice to omit curly braces?

Question

Why does everyone tell me writing code like this is a bad practice?

if (foo)
    Bar();

//or

for(int i = 0 i < count; i++)
    Bar(i);

My biggest argument for omitting the curly braces is that it can sometimes be twice as many lines with them. For example, here is some code to paint a glow effect for a label in C#.

using (Brush br = new SolidBrush(Color.FromArgb(15, GlowColor)))
{
    for (int x = 0; x <= GlowAmount; x++)
    {
        for (int y = 0; y <= GlowAmount; y++)
        {
            g.DrawString(Text, this.Font, br, new Point(IconOffset + x, y));
        }
     }
 }
 //versus
using (Brush br = new SolidBrush(Color.FromArgb(15, GlowColor)))
    for (int x = 0; x <= GlowAmount; x++)
        for (int y = 0; y <= GlowAmount; y++)
            g.DrawString(Text, this.Font, br, new Point(IconOffset + x, y));

You can also get the added benefit of chaining usings together without having to indent a million times.

using (Graphics g = Graphics.FromImage(bmp))
{
    using (Brush brush = new SolidBrush(backgroundColor))
    {
        using (Pen pen = new Pen(Color.FromArgb(penColor)))
        {
            //do lots of work
        }
    }
 }
//versus
using (Graphics g = Graphics.FromImage(bmp))
using (Brush brush = new SolidBrush(backgroundColor))
using (Pen pen = new Pen(Color.FromArgb(penColor)))
{
    //do lots of work
}

---

The most common argument for curly braces revolves around maintance programming, and the problems that would ensue by inserting code between the original if statement and its intended result:

if (foo)
    Bar();
    Biz();

---

Questions:

1. Is it wrong to want to use the more compact syntax which the language offers? The people that design these languages are smart, I can't imagine they would put a feature which is always bad to use.
2. Should we or Shouldn't we write code so the lowest common denominator can understand and have no problems working with it?
3. Is there another argument that I'm missing?

Answer 1

Actually, the only time that's ever really bit me was when I was debugging, and commented out bar():

if(foo)
  // bar();
doSomethingElse();

Other than that, I tend to use:

if(foo) bar();

Which takes care of the above case.

EDIT Thanks for clarifying the question, I agree, we should not write code to the lowest common denominator.