- Please include evidence in your answer. This question is not opinion-based.
I've heard that mathematicians sometimes don't read proofs.
The following is a quote from mathoverflow.
... I think a vast number of mathematicians do not read the proofs, in particular do not verify the details of (all of) the results they cite.
A mathematician I know also says that he sometimes uses theorems without understanding the proof.
I guess that mathematicians in the old days (~19th Century?) read proofs.