Maybe it doesn't really work that well in practice. I guess the idea is that if you wanted to rest your feet and have someone serve you all fancy-like, you could. I like it because it looks great. The soft feel and rich textures of ottomans contrasts nicely with a melanine, metal, or wooden tray. The objects in the tray are easily accessible, but still feel neat and contained within the rim of the tray.
And you TAA-dwellers should like this combo too, because it's a great way to get a lot of different uses out of only a few pieces.
First, using an ottoman as a coffee table gives you a lot of flexibility. Ottomans are usually smaller and more moveable than a traditional table, which is perfect when you don't have a lot of space. Many ottomans have built-in storage space, another plus when you're constantly looking for places to hide your stuff. And finally, they can also act as extra seating when you're got company callin' on you and your TAA.
From Beach Studios, Carolyn Barber, and Carolyn Barber again via Decorology
Put a serving tray into the mix and you've got even more options. Ottomans usually have nice, poufy cushions built in on top, and it's not exactly the steadiest place to display little objets d'art. That vase is going to go right over if you try and put it on a tufted velvet top. But plunk down a tray, and ta da! Instant hard, even surface.
Selina Lake, The Office Stylist, PB Teen
The best part is, of course, is being able to remove the tray to use the ottoman for the functions described above. It's a coffee table! It's a place to sit! It's a place to put your feet! It's a place to hide the TV remote and the trashy OK magazine you were reading!
Aren't you so cute and clever? Now take this tray and get me a drink. Move, dammit!