Google Docs is one of my most used tools, particularly since we are a 1 to 1 school utilizing Chromebooks (and students can turn docs directly into Canvas).
The affordances of Google Docs are many. First, students can work together at the same time on a document. Gone are the days of one student working feverishly while the others in a group watch them. Now students divvy up responsibilities and they tackle their part all at once. A constraint is that it takes the students a little while to figure out how to work on a document at the same time without getting in each others way.
Another affordance is that Docs save automatically. How many times in school did you lose everything because you failed to save it? This feature alone makes it worthwhile to use with middle school students who sometimes can be forgetful. Additionally, I can create an assignment in a Doc and have the students make a copy so that they have everything they need to get started.
It is also a simplified version of what Word can do. This is excellent for younger students. However, I wonder if older students would be better served using Microsoft 360.
Additionally, the students can share documents with each other and with authentic audiences with the click of a button.
A constraint is that it is possible for one student to mess up another students work. However, Docs has a feature that allows you to see (and recover) past versions, as well as who did the editing. This serves as a deterrent as soon as students find out that you can discover who does what.