Work in big, ugly spreadsheets
Spreadsheet work is already soul-crushing enough. Do you really want to make it worse by struggling with data entry and formulas on a touchscreen display?
Store untold gigabytes of data
Even if your tablet comes with 128GB of native storage and a slot for a 256GB expansion card, you're looking at far less than 384GB of storage after you account for the footprint of your OS and native apps. This is not civilized living.
Upgrade and repair your hardware
PCs take a bold, defiant stand against our disposable consumer culture. Components that fail can be replaced. Parts that can't keep up with the latest applications can be swapped out in favor of better performers. Even laptops can be upgraded to varying degrees. But tablets? Not so much. Even if you could penetrate their hermetically sealed shells, you wouldn't be able to upgrade or replace any of their components without herculean hacking efforts.
Live a life free of shattered screens and pilfered hardware
Desktop PCs (and quite a few desktop-replacement laptops) aren't very portable, but this can be a net positive, as they rarely go places where they can easily be broken or stolen. Tablet screens shatter so often because users toss tablets around with relative abandon. And tablets get stolen in public because they're relatively light--and concealable once the hardware has been lifted. Sure, a thief could grab your Alienware gaming laptop from your table at Starbucks, but I'd like to see him sprint down the street carrying that 12-pound computer.
Run a social media command center
Tablets are great for scanning Twitter, cruising through Facebook, and even posting short updates to either service. But if your job (or--gasp--lifestyle) depends on consuming and posting massive amounts of social media, you'll need a real computer for the job. Throw in Google+, LinkedIn, and Pinterest, and a desktop PC becomes de rigueur.
You can't take your PC with you wherever you may stroll, hike, or wander--but this isn't necessarily a bad thing. Sure, your PC tethers you to a desk, but it also allows you to leave technology behind when it's time for socializing--or a period of quiet contemplation.
Think about that the next time you're enjoying a day at the beach, and some D-bag starts playing Angry Birds on the spot right next to you. Those squawking, chirping, tweeting birds have never been more annoying, have they?
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