These days, you need a lot of different logins. That's a lot to remember, so most people look for the easiest way to handle it. For a long time, the easiest option was the password manager built right into your web browser.
This feature lets you get into sites without typing long, complex logins. However, this widespread convenience has hidden a basic security problem in how web browsers work. The convenience you get day-to-day isn't worth the big, ongoing risk of someone taking your private data, which is why some people use BitWarden.