We see that Bitcoin is dropping much less because of the planned Trading-Stop in South Korea than other AltCoins like Steem.

Bitcoin has no other function than being a global ledger which can be used basically only for payment purposes. If there was no exchange anywhere in the world to allow it to be changed to fiat, there would be no reason to hold it.
Generally this payment function has been quite affected anyhow, as high commissions and slow transaction really render it unusable. Still people buy it though because of the strong brand and great liquidity.

Currencies like Steem could survive such a global trading-stop, if the social media outlets where it is been run, like Steemit would increase in popularity and having influence in that community would be something quite valued.

I think the majority of Alts have some other usage than just being money. Ethereum can be used for smart contracts and so on, allowing for systems like Veritaseum to run, which represents an independent value as well.

China

The last time trading was forbidden was in China. Did it have much of an impact? I suggest not, it reached All-time-highs after that... I guess that this time it will be the same. This article is about a global trading-stop with no country left to allow it. It does not seem though that Japan will back-flip. But if every country wanted it to stop, Japan could be under a siege. With sanctions and everything.

Mining-Stop

A short comment about the mining-stop in China.... it is ridiculous to have PoS coins drop stronger than PoW coins because of it. Even PoW-coins should not be affected, only the miners in China negatively and the miners outside positively...

Disclaimer: Everything here is no investment advice and just my opinion.