Looking at how it is in my country, air quality data is too fragmented currently for weather apps to include reliably. Some cities don’t have any sensors with public data, some have only private ones or private ones that give data only via their manufacturer paid API. Those private ones can also be anywhere, so may not provide good data (looking at them here I sometimes think people put them inside their homes) and can be turned off anytime. Only a handful have government sensors with public API.
Yes, just like on a phone you need screen lock (password, PIN or pattern) in order to use it.
There will always be such requirement on Android, since from what I remember screen lock’s pass/PIN/pattern is somehow used in the process of getting encryption key that decrypts and encrypts data such as Google Pay payment data.