I think because it’s the equivalent of cherry tapping to use a well-known and not-that-powerful magic to do the impossible, and Voldemort showed himself to be that kind of perfectionist.
Judging from the quotations that top the TVTropes page, Alan Rickman tends to play characters who engage in cherry tapping. So shouldn’t they be suspecting Snape?
I think because it’s the equivalent of cherry tapping to use a well-known and not-that-powerful magic to do the impossible, and Voldemort showed himself to be that kind of perfectionist.
Judging from the quotations that top the TVTropes page, Alan Rickman tends to play characters who engage in cherry tapping. So shouldn’t they be suspecting Snape?