Because Microsoft Excel is not a text editor. Seriously.
This is a followup to the previous post, inspired by Ethan Banks of Packet Pushers. If you do operational networking at all, you deal with text files all the time: logs, debug output, configuration files, command line diagnostics, and more. I'm constantly amazed when I see people open Word or Excel to do their text editing, often one keystroke at a time.
The number one reason to learn basic programming is to automate that stuff. Personally, I use a combination of traditional Unix shell tools and Python to get the job done, but you could probably do it all with one or the other.
There are lots of other reasons to learn programming too, many of which will be discussed on an upcoming Packet Pushers episode. But if you don't believe any of those, this one alone makes it worth the effort.
Step away from the spreadsheet. Do it now.