As others have pointed out, that mat is solely for sound dampening, not that it does a good job of it.
However, this misconception might come from the other chevys back when they switched to galvanized metal. At the time, no paint formulation would stick, and paint would flake off like dead skin. This was most apparent on the hoods and fenders of vehicles due to differential heating of the metal and paint. An insulating mat that blocked some of the heat reduced peeling drastically. However, since things can catch on fire when exposed to exhaust temperatures, manufacturers opted for asbestos or fiberglass mats to prevent fire in the event that the matting should fall on the engine.
Over time the paint issue was fixed, but another pleasant effect of the mat was sound dampening. Lifter tick was a common occurrence on older engines without hydraulic tappets, even as soon as 40K miles on some engines. Since thin absorbent mats work wonders on reducing high pitched sounds, the mats stayed in order to help quite that undesirable noise.
Advances in engine technology have greatly quieted valve train noise to an acceptable level even without absorbent mats, but the mats still reduce noise further. Think old ford pickups that have huge valve noise due to being beat up. That is similar to how many cars sounded back when the mats were being used for paint protection (not as bad, but still similar).
