I've always have left a "generous" boarder to all my prints, even in the days of silver-gelatin, C-prints, Cibachrome, & dye transfer.
Part of my reasoning is on account of print handling and part was an aesthetic decision. I always thought when the prints were unmounted, they simply looked better with some "air."
Nothing has changed for me in digital, other than the dimensions of the paper: 8.5x11 vs. 8x10; 13x19 vs. 11x14. I still prefer a border though now I have more real estate to leave behind. With the bulk and costs of mounting, I constantly reuse the same frames and matts regularly so many of my prints are simply put on the wall with push-pins, rather than mounting and framing. Cheaper, faster, more efficient for me.
I also use my margins to imprint a brief title/caption and imprint my copyright date + name as part of my print templates.
I use several templates to create my master prints and each has an ample border. Nearly all my work fits on just 3-4 presets, one set for vertical images, the other set for horizontal. It's got the paper profiles and sizing as part of the preset so I can produce portfolio or exhibition prints quite quickly.
In the good old days, like John Nollendorfs said, it was used as a bump & chemical buffer, note taking area from what we once called engravings, and an area to use to handle the print. Though the trend at one time was to produce borderless 8x10-11x14-16x20 prints, my images seldom cropped to those once standard photo paper sizes and I learned to simply compose in-camera and print the full image.
As my work evolved and I worked toward efficiency, I started printing using just a few canned sizes and that's saved me a lot of time, effort, money in that all my matting and framing becomes universal, rather than custom-cut for every crop. For some this is limiting, but once one developed a good compositional habit, it pays off quite well.
