There are actually key/value stores that solve this securely, such as Hashicorp Vault.

The issue isn’t that it can’t be done but more that most people either don’t already know it can be done or don’t want to invest in the infrastructure to do it.

Regarding the latter point, for self hosted solutions I can sympathise a little and it’s really a question of risk analysis. But most cloud computing services do offer their own secrets management service.

(not affiliated with Hashicorp and other services exist).