In my college Drawing I class we started off learning with pencil. It seems this is the norm. So why this is was a mystery to me until I started working with the materials then I understood.
1. Pencils are cheap. A high quality pencil is under $2. You actually don't need a huge pencil set to start. I favor the soft pencils so I worked with 2B, 4B, and 6B. Most basic pencil sets come with various H pencils, I have no use for them personally. Pencil sets are often about $10 or even $15 if you buy one that has an eraser and a sharpener. To me the best investment is a high quality sharpener, a kneadable eraser, a white eraser (rectangle shape), a chamois, a 2B, 4B, and 6B and a 2H if you simply must have that hard thing, perhaps for base sketches. You can get all that for under $20 which is low cost as far as fine art supplies goes. Therefore it's affordable for a college student or anyone on a budget.
2. Pencils are easily portable and pretty durable. Pencils do not melt. They do not shatter and break apart. All you need is some basic care such as not dropping them on the floor or slamming them around. They do well in dry weather and in humid weather, in heat or in cold. They do not dry up or erode over time, you can use a 50 year old pencil just fine. Not all drawing supplies are like this!
3. Pencils are clean to work with. The act of putting pencil to paper is clean so you can do this in a public place, in a car, on your couch, in bed, or anywhere else without muss and fuss. As you use the pencil it does not make dust that falls off onto the surrounding surfaces. When smearing around the pencil on the paper you should use chamois not your finger. The only possible mess is if working on large paper you may get a dirty hand but the graphite comes off quickly with plain soap and water.
4. Pencil drawings hold up well in storage. After making a pencil drawing there is just some risk of rubbing off onto the page next to it. Other than this no special storage is required. The pencil will stay on the paper nicely without special storage needs like chalk pastel or charcoal requires.
5. With one pencil you can get a lot of value shades in your drawing. The same cannot be said for paint. One marker cannot do a full range of value either. By erasing back to plain paper, you can get white without the use of a white pencil.
1. It's hard to get a true black. You can use an ebony pencil for this or a charcoal pencil.
2. It's hard to get a tiny bit of white, erasing can be challenging for a teeny spot, so you can use a white conte crayon pencil if you must.
3. If you don't use a decent quality sharpener you will go through your pencil faster and you might not be able to get a sharp tip. Spend the $10 or so to get a decent sharpener at a fine art store.
Speaking from my own limited experience these are the benefits I see to using pencil to learn to draw with.