Absolutely Not
It depends on you. If you want to display your talents and works then it can be a preferable choice. If you are comfortable without it, then also it is completely fine. :)

Well, this will completely depend upon the will and wish of the user.
If you want to be a bit more informatic about your contributions and developments, then it might take approximately half an hour, which includes the rearrangement of the components as per the needs and sense of design of the user.

If you are using any readme maker, then it might be a matter of 1 to 2 minutes and then the rearrangement and extra stylings can be the time taker.

My personal GitHub Readme took about 2 and a half hours to complete as I didn't use any Readme maker and I have a great amount of dilemma in styling. I keep on adding minor updates or changing some kinds of stuff but that shouldn't take more than 2 mins unless you are going to make a lot of changes!

😎😁

A Readme profile is a dynamic portfolio of the user. This gives an idea about the technical know-how of the user to any viewer of the account.

Here are some listed benefits of a GitHub Readme:

1. Displays a lot of information about the user and works as a dynamic portfolio.
2. Makes the account look attractive.
3. Helps the user to keep a track of his/her progress.
4. Brings out the true potentials of the open-source as several tools used by contributors are effectively used.