You know, I had a comment earlier about the importance of death rites being broadly lost on the young (and without meaning to sound pejorative, I have to believe that you are relatively young). I had thought to myself that I was perhaps being unfair -- surely even a child understands the importance of a funeral? -- but your comment shows that I wasn't wrong.
So as it apparently does need to be said: we're humans -- we mourn our dead. That is, the black bar denotes death, not tragedy; when we mourn those like Wirth who lived a full life, we can at once take solace in the fullness of a life lived and mourn that life is finite. The death rite allows us to reflect on the finiteness of our own lives, and the impact that Wirth had us, and the impact that we have on others. You are presumably too young to have felt this personal impact, but I assure you that many are brought back to their own earliest exposure to computing -- for many of us, was Pascal.
Again, RIP Nik Wirth; thank you for giving so many of us so much.