First, I need to clarify that I’m a fellow user like you, and a volunteer moderator, not a Wyze employee.
I see a lot of your point.
One value of the sensors is to reduce false alerts if you are really only interested in motion of warm bodies or of doors opening. There are many comments on the forum from people who are annoyed by having to review a motion alert only to find it was caused by a change in lighting. Using a motion/door sensor to trigger an alert and only look at the video in those cases will make a lot of those folks happy.
Another use case is when you want to know if someone has gone into an area that you don’t necessarily want a camera, such as a bedroom. Say you have a camera at the bottom of the stairs, but you really only want to review the video if someone had gone upstairs and entered a bedroom. The motion sensor or door sensor could accomplish this.
I’m sure there are hundreds of other applications that imaginative folks will come up with. For example, I’m going to try putting one in my mailbox to get an alert when my mail arrives.