Different projects I'm involved with protect profiles for similar and yet quite distinct reasons.
PGM protects pretty well everybody since they only deal with ancestors who came to the colonies from 1630 to 1640. This keeps anyone from giving them spurious parents. Many interesting lines were created for these people in the 1800's, and even now we're still sorting out which lines are truth and which are fiction.
Dutch Roots also protects everything up to 150 years ago. I see two important reasons for this. First, even though it's fairly easy to connect people born before 1811 with their parents through patronymics, it's very easy to give them the wrong parents. Therefore most of us involved with Dutch Roots have done a lot of extra research to "prove" family connections in a variety of ways. For example, when Westfries Archief released about 200 years' worth of notary records a few years ago I went through them carefully and discovered about 25 connections between parents and children that I personally had wrong on WikiTree. Most of these have been connected wrong by genealogists for over 70 years. Others have been in dispute that entire time. We don't want that work destroyed by a well intentioned newcomer.
Secondly, in 1640 there were about 30,000 people in what is now New England, and at least several thousand people are working on their lines in WikiTree. In the meantime, there were about 2 million people in the Netherlands and probably about 100 people are presently working on their lines in Wikitree. I am blessed that a genealogist started work on my father's father's side of the family over 100 years ago and that many others coming from the same town have become genealogists. That means I'm the only person presently working on about 60% of my own Dutch genealogy instead of most people who are the only ones working on about 75% of their Dutch genealogy. This still means I have created at least 9,000 profiles. I'm not able to manage all of them. There are many siblings of my ancestors that I create a profile for and then turn over to Dutch Roots Project WikiTree to manage. Otherwise I would have to orphan them, and it never feels comfortable to me to leave them orphaned.
So what are the reasons people want certain profiles to be project protected? It's certainly important to protect the ones for famous people. And it's certainly important to protect those for which parents may be disputed, after the proper amount of research has gone into them. But others may want still more, even everything, protected if they're creating too many profiles to manage. I know I have between 500 and 1000 profiles of people living in present day Germany that I feel responsible for and thus manage. It would be a relief for me to give many of these to a German Roots Project WikiTree to manage. However, this would create a lot of work for you, Kylie. Ask Bea Wijma how she manages it for Dutch Roots if you consider this route. I know it creates a lot of extra work for her.