10 points
Because it doesn’t really solve much. After every update of external libraries, do you go through all the diffs to see if there is malicious code? Of course you don’t. And even if you would, it’s not even always possible to spot it. So all locking packages does is postpone the problem to when you eventually update. As an added bonus, you’re now vulnerable to all the legitimate issues that get fixed in those updates you’re not installing regularly.
