The Werewolf's statistics are that of a CR1 monster, even though it is listed as CR3 in the Monster Manual, presumably as a result of playtesting.
By my personal experience with pop culture, Werewolves in fiction tend to be susceptible (not vulnerable, mind you) to non-silvered damage, but especially vulnerable to silver. Given that, it seems kind of absurd that a 20th level Barbarian with a standard greataxe can't even put a scratch on a lowly monster with theoretically CR1 stats. Recently PCs recruited the town militia to fight off a werewolf, only to find that their weapons literally do nothing. And that doesn't make sense.
In regard to my first point, believe that hypothetically, if the werewolf weren't totally invulnerable to most non-silvered damage, even playtesting wouldn't have brought its CR as high as 3. Not only that, but removing the immunities would make it considerably more accessible to parties of a greater variety of levels.
I feel like the designers had every opportunity to give the Werewolf resistance instead, because not only would it solve the above discrepancies, but let's face it: Werewolves just aren't cool enough to be that invulnerable. But the designers didn't make that choice.
What reasons have the designers given for this design choice?