why is Photoshop used for wireframes?

[cave_cat]

question - what are the reasons behind use of Photoshop for making of wireframes? Why not instead use a vector graphics program such as Corel Draw? Is this a matter of tradition, or are there serious reasons why specifically Photoshop functionality is essential to wireframing?

Also, where can I see some examples of good wireframes for an existing website, so that I could learn from example?

[Light Speed]

I guess it's all down to preference.

Some use one program, others use others, I don't think there's really an answer for this.