USPS tracking percent delivered

I’ve been sending and receiving tracked packages and envelopes my whole life. Never lost a package without the tracking showing it was delivered and when. In those cases someone stole it from the mailbox or step. In one year we’ve lost 3 out of 5 on different weeks. Doesn’t the USPS keep track of this? Can they see how much worse it’s gotten? A percentage maybe? It’s happening to everyone I talked to. Obviously they don’t know with untracked envelopes. Who is stealing? What role is their job? Why is there no solution? If it was only me I’d say who cares, but it’s not.