1. Password managers provide additional options
A key difference between using a stateless password manager and a password manager is that password managers can store additional data such as
- Security Questions
- Credit/Debit card numbers
- Id card numbers
- Cryptographic keys
- WiFi passwords
- API keys, etc...
2. Existing passwords cannot be accommodated
Password managers can accommodate existing passwords. But a Stateless password manager will force you to change passwords for all your existing sites.
This is very important if you want to store passwords for any account where you are not authorized to change the password. This can be a shared office mailbox, server password, etc...
3. Deterministic password generators cannot accommodate varying password policies.
Some sites will need mandatory symbols with passwords but some sites do not allow symbols in passwords. Some websites like Payback support only numeric PIN.
Users either need to tweak the generated password or change settings. In either case, they need to keep the tweak or settings in memory which is not good.