The Universal Carrier is what happens when you strap some kitchen foil onto a chickenwire frame, squeeze an engine inside, and fit the whole thing with tracks.
Bullets will penetrate the UC with great ease, wittling away its life at an accelerated rate. It's a good medium-machine gun carrier early game, once it recieves one of it's two possible upgrades, the Vickers or a flamethrower. However, it quickly falls prey to literally anything, from grenades, to panzershrecks, and god forbid anything with a cannon.
A possible for a UC that has survived into the late game somehow might be carrying heavy engineers about. However, if you have upgraded it, it will be incapable of doing so. Furthermore, late game tanks will destroy this frail vehicle just by aiming at it, making it an expensive version of the russian Zis transport truck, with a restricted compartment.
Another problem with the Carrier is it's size: it's so small that it can only carry one squad of infantry, compared to most faction's two squads.