The original shell was the bourne sh. It had limited capabilities and was designed to lean very heavily on external programs. It had almost no built-in functions. The authors of awk wrote awk in this environment. And they stated roughly that awk was intended to greatly extend the kinds of shell scripts that can be written.

The first shells were written before awk was written. awk was never intended to be a new shell. awk was intended by its authors to work with shells, not replace them.

Both awk and the shells are now much more powerful. You can write stand-alone awk programs. And you can even write stand-alone sed programs for that matter. But both awk and sed are generally used inside of a shell script.

When I wrote in the the bourne shell, I leaned on awk very heavily. But I always saw awk as a crutch for a weak shell. Now that I have switched to the korn shell, I almost never use awk anymore.

But that's just me. Other folks really like awk and use it extensively. Unix has many tools and there are many ways to do most things. You really need to survey the tools and pick your own favorite.

I will say this though, no one uses awk for a login shell. awk programmers will need to know a shell well enough to at least log in.