Laws in Spore are not for the protection of lesser mortals. Even if there are laws prohibiting service charges who is going to enforce
A Singapore restaurant registered to collect 10% service charge, that's billable and payable. The restaurant must satisfy certain criteria before it can register to collect it. This must be accounted for separately on tax returns. For better than expected service appreciated, customer is free to allow a keep the change or award extra tips. That's non-taxable and is up to the employees' arrangement and agreement, i.e. individual pockets individually or pot together, then split and share.
The US system of all tips for services is to bypass the tax returns. Technically, tips have to reported as income too but there's no way cash tips pocketed or potted can be traced. The employers are fine with that too since they can set a lower basic salary and let the employees earn and sort out the tips themselves.