Probably a visual convention for clarity in illustration. As for ease of drawing, that depends on the situation. By the early Renn. (1450) they were obsessed with the new visual high tech (linear perspective). Putting an object like gauntlets into that system, would scarcely be easy. (Same reason the Artists of the period spent so much time drawing complex goblets and silly hats, the proficient people were showing off)
On whether anyone would have had armour, must have had gauntlets, perhaps not everybody. The gauntlets, due to the fairly small size and complex articulation were amongst the harder items to make. So these would have been very high cost, some were even test masterpieces for master entry into guilds. To give a sense of how complex these were, some of the armourers of the period, moved into making the eras high tech wonder, the spring driven clock. (Nuremburg eggs for example). Wasn't an accident that the gauntlet makers and clock people were often in the same centers like Nuremburg.
As to damage to the hands. Quite true, have been whacked a few times sparring, yeesh, even with heavy gloves. Would wonder if the side ring longswords and such, were a development in part- fostered by those not having full harness, or who chose to not wear gauntlets to have better control.

