It is because there is no quantum computer and yet advanced one that will exist for now (and estimated to 2030 or more) that will be a threat to bitcoin. Although they will later be produced but when the right time will come, bitcoin developers will do something that will make it impossible for the quantum computers not to access people's private keys. They still know that it is not yet necessary for such upgrade yet.
My doubt in this regard is whether a fork will have to be made or resilient wallets will be created and somehow we will have to migrate them. I guess since it is not yet known exactly what we are up against it is not possible to create the solution in advance.