"type and see what it does" is a strawman. Some people absolutely do program this way, I don't deny that, but there's a huge gulf between that and the levels of verification it takes to ensure that a large program really does behave as intended. Typos, minor oversights, unforeseen consequences of refactoring. . . the number of things you need to guard against is immense, and nobody can be operating at 100% 100% of the time.
And very few people can know 100% 100% times. We build software on top of abstractions. Abstraction leaks, abstraction breaks and abstraction isolates you from "know what you are doing".
If you build software in C, you will build abstractions in C, and debugging / analysis tools help to understand these abstractions.
