The benefit is the miners are fungible. If one miner wants to enforce unusually high fees or restrictions on what kinds of transactions can be sent (such as whi

The benefit is the miners are fungible. If one miner wants to enforce unusually high fees or restrictions on what kinds of transactions can be sent (such as which countries can send funds between each other, etc), then it just means that if that miner mines a block, some transactions have to wait an extra block to get mined by a miner without those extra restrictions. And it will be more profitable for that miner because of the extra transaction fees, so in practice miners don't impose extra limits.