You’re making a game set in modern times where you need whole bunch of modern standard weapons. You come across such pack on market place. It perfectly fits your bill. 20-30 modern weapons, modeled, textured, with materials. etc etc. Ready to use. Price $50 - 200.
But you want to be ambitious and say, nope, I’m not gonna use them, is cheating and makes me look unprofessional, lame and weak in general form. Instead you make exactly the same weapons yourself. Instead of spending $50-200 you spent a month (if you work fast) and at the end of month you’ve came up with exactly the same pack, but instead of buying it for $50 -200 you made it yourself - at least 8hours per day, at least 24 days = 192 working hours (at least), on something you could have bought in 5 minutes and spend additional day or two on modifying it, that is adding custom scratches mark, discoloration etc.
Do you really think game player will say, wait a sec! I saw that AK-47 in some other game also set in modern times and it looked exactly like it. That is, it looked exactly like AK-47, what a lame game it is!!!
Yep, right. It looks exactly like Ak-47 because it is AK-47 and IT SHOULD look exactly the same in any game which uses AK-47 as a weapon model!
While I agree, there is actually a lot of wiggle room in example. For instance Killing Floor benefits from a unique AK-47 model by showing incredibly detailed animations during slow-mo. Including all the moving parts and details required in, say, an AK-47 in Call of Duty wouldn’t make sense.