Of course we all have different reasons for doing things in a certain way. Luckily!
For some images I like to include the black border, for other images not. Sometimes what happens on the edges of the image is so important, then every millimeter more image can become important. Sometimes the image falls apart without a border. Sometimes a border is too much for a certain image.
For some people who do not have the experience: To print a border around the image is generally done by including a little bit of the negative borders around the negative, on all four sides. Remember the negative is transparent around the image, you just expose light on to the paper. One way is to use an easel and, when masking off image, you just include a little bit of border around the image. That way will give you sharp and straight border lines on the outside. On the inside the border lines are never as straight, sometimes image and border melt into each other and also, on the inside of the border, the corners are often rounded - giving this wonderful analog feeling.
Another way to print borders is with a negative holder or mask, that has a couple of millimeters more opening than actual negative size. This way you will get slightly fuzzy outside border lines, not hard straight. Leitz Focomat 1C and Valoy II negative masks are great for that. There are enlargers with negative masks that make it possible to create a border by closing four 'flaps' close to the image. Often this results in quite dominant borders, not really my thing.
To print without a border and use a black marker is something I would never consider. The black of a marker will always differ from the black of photo paper. And, even though on the marker the word permanent is used, you never know what that black marker's ink will look like some years later. There exist many fiber prints, signed in the white around the image, that have discolored or faded hand writing. The nightmare of the photo dealer: a beautiful print with a fading signature.
One of the reasons for borders, including their small faults, is the obvious analog feeling: this is made by hand, the next time it will look slightly different. It is like life, never quite perfect. That perhaps being my main objection to digital printing: it is too perfect.