No, students are already forced to use Canvas enough as is. This is enterprise software, it's not a consumer phone app. This is nothing to do with "engagement".
This is to do with FERPA which requires that student grades be kept private. There is a small but still a significant legal risk that someone else such as a parent or roommate could have access to a student's email. And so to avoid even the possibility of a court case, schools prefer to play it safe and display grades only to a user they can authenticate directly.
This doesn't have anything to do with common sense, it's simply about legal risk. And it's not about security in a broader sense, it's specifically about privacy FERPA legislation.
