Still, even getting that deep into it, there are 1 or 2 month stretches of time where I do no scripting at all. I might be deploying a 100TB SAN somewhere, building Oracle database clusters (using automation scripts I wrote months ago in cfengine), doing firmware updates, fixing network issues, helping VMware admins figure out their boxes, etc.
The problem with a sysadmin's life in general is that there is way too much stuff to do to focus on scripting or coding 8 hours a day. Some of us love that stuff, but when you've got a brand new SAN, blade chassis, or servers to deploy, they don't just deploy themselves. There are probably only a few shops that actually embrace the sysadmin coder, or devops as I've heard it called.
Your point about ad-hoc scripts is well taken. I use one-liners on a daily basis, even for general computing tasks like renaming files, or to manipulate data using awk or sed. This is not what I would call real scripting, but it does require a fundamental understanding of the tools.
Perhaps I'm biased because I spend so much time in front of a computer, but I can't imagine ever getting rusty at scripting unless I'd left the industry totally and gotten rid of my computer. There's simply too many simple tasks that are made much easier with ad-hoc scripting. I don't think I could make it through a week without writing an ad-hoc script, be it something as simple as transcoding videos to MP4 for playing on devices, finding some files with specific criteria, renaming and classifying photos based on EXIF data, etc.