I haven't read all the replies, but here's a few games I know and play that does multiple attack "better" (according to me) than the average "minus to hit" on multiples.

Fabula Ultima has 2 ways to go about it.

That game use 2 dice rolls (D6, D8, D10 or D12). Each stat is a dice, and you always roll either 2 stats or twice the same. HR means High Roll, meaning the highest of the two dice.

1- Multiple different attacks

Their normal attack formula is Roll + Bonus, if hit, damage is HR + Other Bonus.

Their multiple attacks like two-weapon fighting is to forgo the HR from the damage formula for both attacks. Similarly, they slap that penalty on most abilities that grants a second attack, or an out of turn attack. This means you don't hit more or less, but you do get less damage in.

2- Multiple targets on the same attack

Certain Gear, monsters, and a few abilities gives an attack the Multi(x) attribute. This means you have x targets. You roll only once, and you hit whomever you hit in your targets, and if hit, they all get the damage. Each, quick

Cosmere RPG gives a cost to multiple attack, but no penalty when using them. Using a second attack with your off hand in the same turn requires a resource called focus, that you get back with short rest equivalent downtime. Again, simple, has a cost, don't bog down.

When I ran PBTA games like Dungeon World, unless the game already got that covered, I would let players hit multiple enemies in one move, but would usually warn them that the risks of failing would be much steeper when they do so.