This is a good question. In our age of computers, it is important to ask what the benefits of human production are apart from computers. When it comes to this question, there are several advantages of human-drawn sketches.
First, for all the benefits that computers have, there are not perfect. Systems could go down and there can be unforeseen glitches. This can completely shut down an investigation for a time.
Second, there can be power outages, which means anything digitized is contingent upon electricity.
Third, believe it or not, computers are not as intelligent as humans, especially in terms of sketches. If you need proof, think about the advancements in artificial intelligence. There is very little gains. The human mind has so many nuances that computers cannot capture.