I would say it is only because you could mess up the surface of your table with most anything you do. What you choose to use as a craft mat is up to you.
I use a wooden surface, some use glass, others buy expensive mats, but if you are on a budget, you can find self healing mats in other areas of the craft stores for less money. Basically the same thing they are just less.
I would say it is also safer to use the right tools for the job. Mats are protective surfaces and do many jobs. They not only protect your work surface but they also can keep you from having an accident. You want a surface that won't move about. You want a surface that can take any technique you throw at it. That is why I choose an old wooden surface. I cover it in paper. It doesn't move, I can cut on it, glue on it, do pretty much everything on it, and it definately protects my work surface.
Some use glass tops on their tables. Others use fixed self healing mats of all sizes. Others have a specific mat ofr every technique. It just depends on your budget and scrap style.
I know when I do paper piercing, cutting, or use any other sharp tool, I don't want anything to move around. I also don't want my table to take that kind of damage. There are mats for many techniques but I choose a little different option because I don't have to buy a mat for every occasion.
Short answer... I believe a craft mat is needed unless you find a different creative idea. There are many options out there for every preference.
I'm one that uses a glass 'mat'. It is actually a great big glass cutting board that I purchased at Walmart... (I think!) I prefer it because it's not only easily cleaned, it is also what I prefer to have when using an exacto knife. My circle cutter also requires a glass surface. With the glass, I don't have to pull out another 'tool' to change tasks.
I use a silicone baking mat but not for any cutting or projects with sharp tools. The silicone baking mat was cheaper than the Tim Holtz craft mat and it washes easily (even goes in dishwasher). It works well with misting, stamping, and heat embossing. I bought mine online many years ago but I think you can find them at Target, etc. If you are watching how you spend your craft budget, I would say to skip this. You can cut apart cereal boxes or cardboard to put under your projects. Of course, this is just my 2 cents worth.. or maybe with inflations it's a nickels worth now.