Because it's an additional risk that you're aware of and prepared to take when riding your bike simply by riding 'no-brakes'. This means you're also aware that you won't be able to stop as quickly as riding with a front brake. This means that by riding in this way you also pose an additional hazard to other road users. Simple really.
Because it's an additional risk that you're aware of and prepared to take when riding your bike simply by riding 'no-brakes'. This means you're also aware that you won't be able to stop as quickly as riding with a front brake. This means that by riding in this way you also pose an additional hazard to other road users. Simple really.