Yes, why should you? It takes time and is just another thing you have to learn....
But I think the benefits out way those points! Money would be my first benefit. Professional framers can charge you by the meter to cut your mats for you, making it not too economical. You can buy pre-cut mats of course, but I find it hard to buy the colour (and more to the point the size) you want! Artists especially tend not to stick to a specific size for their images.
Multi opening mats are very expensive to have made, so worth looking at cutting yourself.
Whilst we're talking economics.... when you're cutting a mat always keep the bit you cut out. It will make an excellent mat for a smaller picture. That way you make the most of all of your mat board.
Then there's the preservation of fingers! Try cutting a bevel with a craft knife and getting the corners right.... it's not an easy task. A basic mat cutter like the 810 is a great place to start, and is money you'll make back in no time. It's an easy tool to use too.
If you're on a budget, a budding or professional artist or photographer I would recommend having a go at cutting your own mats. Ask your mat board supplier if they have a few scraps for you to practise on so you don't waste your good board.
Have a go, it's really not hard!