> Why don’t they also read your gmail

Boy do I have news for you.

" Microsoft is scanning the inside of password-protected zip files for malware"

https://arstechnica.com/information-technology/2023/05/micro...

The tools in gmail in some sense "read" all your mail in order to classify spam and do things like calendar integration. The extent to which they do other things with the information is .. unclear.

Because your bank doesn't send your password to your Gmail because if they did they know Google would read it.