Why should I use the DIM statement in VBA or Excel

Question

So there is a question on what DIM is, but I can't find why I want to use it.

As far as I can tell, I see no difference between these three sets of code:

'Example 1
myVal = 2

'Example 2
DIM myVal as Integer
myVal = 2

'Example 3
DIM myVal = 2

If I omit DIM the code still runs, and after 2 or 3 nested loops I see no difference in the output when they are omitted. Having come from Python, I like to keep my code clean*.

So why should I need to declare variables with DIM? Apart from stylistic concerns, is there a technical reason to use DIM?

^{* also I'm lazy and out of the habit of declaring variables.}