Sometimes matts are so tight against the skin the groomer needs to take her time to get the blade between the matts and skin. Sometimes it takes very short to very very short blades. Pets skin is sensitive and in some areas it winckles and we definitely need to be careful not to cut the pets skin.  
We all want our pets nails trimmed very short. However in some cases we can't go as short because if the nail isn't trimmed on a regular basis the quick grows longer also and if you cut too short the nail will definitely bleed. So the groomer will definitely cut as short as they can and if done a couple of times on a regular basis the quick will start to shrink back and then the groomer can cut shorter.

Matted pets take longer to shave because some matts are closer to the skin then some other areas on the pet. Also when a groomer shaves down many matted pets the blades used become dull faster and need to be sharpened more often. 
I BUILT MY SITE FOR FREE USING