I have tows (including horse limbers and a variety of horse carts) for twentieth century operational games. There are an awful lot of beans and bullets to haul around on the modern battlefield, and they produce such lovely traffic jams. I aos have piles of fuel trucks, radio vans, repair vehicles, bridges etc.
My nineteenth century stuff has lots of 6mm limbers and wagons (thank you Irregular, also many thanks for the 6mm bearer stands!), although strangely my 15mm Colonial armies don’t have huge amounts of transport apart from mules and camels. A horse cart is a horse cart however, and I’m sure my WW1 and WW2 armies don’t mind lending a few out. My WSS chaps have a rather grand pontoon train.
Even my 54mm chaps have some artillery limbers and wagons, although latter are pilfered from kids cheap plastic Wild West sets.
Real armies are encumbered with tons of baggage which gets in the way and makes their movements somewhat ponderous. It seems a shame not to represent it. I still hate painting horses though, so I have an awful lot of one and two horse carts. Thanks goodness for the internal combustion engine.
"Mistakes in the initial deployment cannot be rectified" - Helmuth von Moltke