A way to link to a specific part of a YouTube video:
WAIT… CAN’T I DO THIS MYSELF BY ADDING THAT BIT AT THE END?
THEN WHY IS THIS HERE?
A) Not everyone knows about it yet, B) even if they do, they forget how to do it, and C) laziness.
It’s funny in this case, but great inventions, products, and services are often born out of a desire to help with forgetfulness and/or laziness. See also this chart: Geeks and Repetitive Tasks.