It came up again: a PC with two weapons wants to do two-times the damage.
The iconic 5e version of this is the two-weapon rogue, and no, they don't want to hit twice to do double damage. Rogues do most of their damage via Sneak Attack. They want more chances to land the one Sneak Attack damage a round they can produce.
This time, I didn't think about the rules-answer, I wondered about the real life answer.
In real life, a second weapon isn't about making a second attack. It is more about being able to parry and feint. D&D doesn't (imho) suitably model parrying with two-weapon fighting, but the effect of feinting is there, in that getting two attacks makes you more likely to land at least one, which is what feinting is about.
What if the victim is wearing armor? What if the thug is a swordsman with two swords? Don't you lose momentum when your next attack is from the opposite side of your body? What about reach?
Momentum is important for attacks relying on Strength. Two-weapon fighting is more often a Dex-based approach, which is more about precision. D&D doesn't get into small differences in reach, so that's not really material.
How are we feeling about this lately?
I'm feeling the idea that using two weapons is wanting to do twice the damage is not really accurate. And, to within the level of realism D&D normally provides, it is fine.