Why do some people have 101 points when they register?

Question

If you look at the recently registered users, you'll notice some start from 1 point and many start with 101 points.

Why?

Answer 1

The answer is found in questions like:

Should all linked accounts get the 100 bonus?
Linked account didn't get 100 rep points

namely, people who already have 200 points in another stack web site get an automatic 100 bonus when they register in a new stack web site.

Answer 2

As for why the 100 points are given, I believe it's because, if you've already earned 200 rep points at one SE site, there's no need to work from the ground up to re-earn the most rudimentary privileges, like commenting, voting, and talking in chat. Presumably, you've already become familiar with how the Stack Exchange sites work.

Without this bonus, some users might be deterred from joining other sites, simply because they wouldn't want to start with a rep of 1 – particularly when they've already been active and contributing members somewhere else on the Stack Exchange.