Switching intensity of LED's
First, this is not a good circuit. The current with the switch open depends on the current amplification factor of the transistor, which can vary widely. If you just want to vary the brightness of the LEDs you could put an extra series resistor (beyond R2/R2, value to taste) and short that resistor with your switch (change R2/R3 to limit the current to your desired value).

The reason that you don't burn out your LEDs is probably that you used a 9V battery, which has considerable internal resistance. In your simulation you probably used an ideal voltage source, which has 0 internal resistance.

Another reason might be that a LED does not die immediately from a high current, it merely has a significantly shorter lifetime.