The fee was always intended to be turned on at some point, but following the community feedback on both the forum and the Discord server, it seemed that people generally preferred to turn it on sooner rather than later. This is why it's included in this proposal - the purpose is purely to better align the product with the expectations of OHM holders.
It's worth noting that once a user's vault is deployed it is locked into that configuration - so turning on the fee switch at a future date will mean that all existing vaults will be grandfathered in at 0% fee.