What do you use your tablet for? Surfing the web? Engaging in some social media humblebragging? Paying your taxes? (reminder)

All of these: perfectly valid tablet activities in which to engage. Tablets sure are versatile little buggers, but there’s one big feature, one that seems so obviously useful, that they’re all – as nearly as I can tell – missing.

No tablets have the ability to display video. No, I don’t mean being able to decode and play back video files; I’m talking about video input. These tablets have some bright, beautiful, and increasingly-high-resolution displays, yet we’re stuck using them to only view content generated internally by the tablet’s hardware and software; why can’t we hook any of them up to external video sources?

It’s not that there aren’t plenty of ways to get entertainment onto your tablet itself, whether that means purchasing and downloading TV episodes or installing native games, but why are we limiting ourselves by not having access to everything else?

I got started thinking about this idea when my mother was moving to a new house and buying some new TVs for it. She likes to have a little set in the kitchen, and I got to thinking about what a waste that is. Or rather, what potential there would be to do things a little differently. After all, a forty-inch-plus living room TV is staying put where it is, but a ten-inch screen in the kitchen sounds perfect for something a little more modular. Replacing it with a tablet would let mom look up recipes while watching her favorite shows, and pop it out of its stand to take with her when on the go… if only tablets could be connected to cable boxes.

Ideally, I’d love to see tablets supporting all sorts of video input, both analog and digital. HDMI input should be as easy to implement as HDMI output, which is already widespread. Analog, on the other hand, gives me pause. You’d need some kind of break-out cable to support composite (and hopefully even component) input. We’d also be talking about a whole bunch of new circuitry, and given the space constraints tablets already struggle with, that could be a hard sell.

I think that’s a shame, because I’d love little more than to be able to plug one of my 3DOs into a tablet for some impromptu retro gaming. The absence of analog support need not kill this idea, though; even if tablets only supported HDMI input, we could always use external adapter boxes that, in a pinch (though a little pricy), could route that analog video over a modern digital connection.

For most of you, analog would probably be an afterthought anyway, so digital is clearly the thing to focus on. Just what could you do with a tablet that accepted HDMI input? Well, besides that aforementioned idea of being a temporary TV in places where you really don’t need a TV residing 24/7, what about as a second monitor for your laptop?

Plenty of us enjoy the luxury of working with multiple displays when using our home PCs, so things can feel a little cramped when we’re out on the go and stuck with a single screen. A tablet, stand, and short cable could be all that’s between us and some mobile multi-screen productivity. Or, if you’re looking to give a presentation to a small group and don’t have access to a projector, a tablet could easily let you share things with them while keeping in control from behind your laptop’s keyboard.

Now sure, use with computers is a special case, and there’s nothing stopping software from filling in for the absence of an HDMI input, digitally streaming screen content over WiFi. That’s still a kludge, though, and with all the issues of software compatibility and bandwidth that could crop up (god forbid you’re running an exotic OS on your laptop), a hardwired HDMI cable just screams “elegant solution.”

The more I think about it, the more upset I am that this functionality doesn’t already exist. Surely, it must have crossed the minds of at least a few engineers tasked with coding-up the HDMI video-out support for any of the many tablets featuring it. Perhaps manufacturers are convinced that too few people would take advantage of video input. That’s a fair point, but there are already plenty of tablet features that go under-utilized, and those are still in place. It’s also not like it would add significant bulk or expense to the manufacturing process.

The cynic in me says “this is all about the money,” that tablet manufacturers want you enjoying new tablet content you’ve purchased just for the tablet, not using your tablet to view content you acquired elsewhere, on another platform. The thing is, I’m not sure how well that theory holds up, as Sony’s sure not getting a cut of Google Play video sales, but I wouldn’t be surprised if there was truth in at least some aspect of this argument.

Perhaps there’s a degree of pride to it all. After going to all the trouble of designing advanced tablet hardware, and delivering the device with a state-of-the-art software package, I could understand how it could be a bit disheartening for manufacturers to see their users turn around and just treat their expensive tablets as little more that dumb screens.

But man, wouldn’t it be neat if this feature actually was available somewhere? I know I’d sure keep it in mind when shopping for my next tablet. What about you? Can you see yourself using a tablet as an external monitor, or is this one feature you could live without?