if you leave your computer unattended for even a very short period of time, it is very easy for an attacker to steal some passwords from browser's lastpass extension. It can be opened without any authentication.
Even requesting a PIN nr, or fingerprint authentication would do the job. As this is for preventing sneak password steal, not for preventing a time-consuming complete hack of account.
Unlike in Android's version, where you are requested to present e.g. fingertrip everytime you open the app (or even app is opened, but switched to an other app then back), it is very useful.
Pls invent such feature for browser extension, too.
ps: log-out after a certain period is time, or log-out when quit from browser are not proper solutions, as they request to re-enter complicated master passwrod everytime. It is not easy, and it may allow to witness the most important master password password at unsafe places.