It is a technique that is quite hard to learn to shave with these things without turning your face into a bloody mess. At least when you're starting with these. Especially if you had / have acne or some birthmarks in your face that make the surface of your skin uneven.

You can shave them off if you have enough pain resistance.

I learned this when i served my country in the military but when i can choose i definitely prefer an electrical shaver because its more convenient, takes less time and is even better (no water and shaving soap required: only a socket once in a while; only change razors every two years) if you invest some money into your device. Today even the cheaper ones are water-resistant so you can shave under the shower without any mirror required which i think is especially convenient and time-saving.

The only downside of electrical shaving vs. these oldschool devices, i can see, is: You almost never can get it that perfect as with these oldschool razors. But only if you are proficient enough with these razors and take the time and concentration for it.