While true that they are light, they don't have Nick, and Crossbow expert is better for getting a bonus action hand crossbow attack.
But they do not have to have nick as long as the other weapon does. For example a hand crossbow and a scimitar.
Attack with your crossbow (attack with a light weapon)
Attack again (with either your crossbow or your scimitar)
nick with your scimitar
bonus action attack with your hand crossbow.
In this case all 4 of them get your modifier to damage if you have two-weapon Fighting Feat. If you have the dual wielder feat you can do the same thing, with the same weapons or any other combo of light weapons as long as one is nick, but with dual wielder you do not get to add your mod on the bonus action attack.
There are also some crazy dual wielding combos that require juggling.
Enter combat empty handed.
Attack with a greatsword, drawing as part of the attack
Drop greatsword, draw scimitar as one free draw.
attack with shortsword, drawing as part of the attack
nick with scimitar.
drop both your weapons
attack with a longsword Versatile using bonus action drawing the weapon as part of the attack