There are no programs written in 100% safe Rust—the std library is written with unsafe as needed. But typically the majority of lines in the program—sometimes even all outside std or some well-audited foundational creates—are safe. Those lines can not directly cause any unsoundness, which has tremendous value.

This has been discussed ad nauseam and this adds nothing new. There's value in the memory safety for the majority of the code even if there are some escape valves ("unsafe" keyword, assembly).