i got a tray 2 years ago for carrying food.
(this tray is out of stock but you can see the 23" x 15" dimensions. don't go much smaller. i got a 17" x 10.6" one first and it SUCKED, i returned it. note that you lose some flat space to the angled sides)
note i linked a BIG tray. there's a bunch of smaller ones that can't even fit 2 plates.
easy to carry more than 2 things at once (this is why i wanted it)
easily carry hot things
easier to keep things level while walking
even just a plate, a cup, and a bottle with a sauce is 3 things and not that easy to carry with your hands. adding a bowl of soup or a side salad on its own plate makes it way harder to carry. and even when carrying just a plate and cup you may have to balance your silverware on the plate and get it dirty.
i started sometimes having multiple different drinks with meals because it's easier to carry 2-3 different drinks at once this way. i drink smaller amounts but sometimes i like the variety. or sometimes i don't know in advance which drink i'll prefer and end up drinking one and not the other, and it was good to have the options (having a bit extra of each, and "wasting" some, is totally reasonable. most drinks are cheap). it just sorta didn't occur to me to have 2 different drinks before i had the tray to put them on and had used it for a while.
you can put food discards (e.g. corn cob, clam shells, bones) on the tray without needing a separate plate or trying to stick them on the side of your main meal plate. cleaning the tray is no problem, but you generally wouldn't wanna put that stuff directly on your table. (unless you're using a tablecloth and clean it routinely, which sounds dumb. )
it's easier to carry a bunch of different sauces/toppings/spices as extra options, even if you aren't sure which you want. you can just try a little of each while eating.
you can set other stuff on the tray, like a towel or iPhone (good for speaker phone calls, and more convenient than taking it in and out of your pocket)
if you don't know how much of a food you want, you can bring a bunch (like in a tupperware) and then serve multiple small portions to your plate during your meal
for people who sometimes leave dishes in their room instead of immediately carrying everything back: if you use a tray once per 2-5 meals, you can then carry all the dirty dishes back at once with the tray.
SAVE TRIPS WALKING BACK AND FORTH
you can eat directly from your plate or bowl while it's on the tray. the tray doesn't take up a lot of extra space. this won't work in all situations. if you have a bunch of stuff and a crowded table, a tray still helps for carrying things to the table and taking dirty dishes back. also if you don't eat at your computer desk sometimes, or your computer desk can't fit a large tray, i think that's bad and you should change it. (i push one of my secondary displays back a bit to have tray space.)
i use my tray most days. A++++++++++++