It makes sense since Samsung has its own payment infrastructure (Apple Pay, Google Pay, Samsung Pay). Although those are for retail payments for in-person purchases rather than app store purchases, I can also see South Korea not wanting to have foreign merchants controlling substantial markets, such as an app store. Those laws probably apply to Samsung as well, if Samsung deploys its own app store.
- Samsung is a major conglomerate domestic to S Korea. LG is a similar congolmerate
- They make consumer appliances and durable goods, similar to how General Electric in the US used to (washer, dryer, fridges, dish washers, TVs) and are on their way to make them "smart" and connected devices
- They compete in the Android phone and smartphone market. LG (another S Korean consumer devices conglomerate) had recently withdrawn from that market.
- They own their own cloud (Joyent acquisition). However they are cutting back on their consumer cloud offering in Mar 2021.
- They own world-class semiconductor fabrication facilities, peers of TSCM and Intel. Samsung produces chips, memory for themselves and other customers. They also produce milspec, secure smartphones for the US military
- They own an AI research team (Viv Labs acquisition, founded by the team that created Siri and sold to Apple)
- They have Samsung Pay
In other words, Samsung has its own flywheel going and controls a national stategic assets (semiconductor fabs). Maybe South Korean law is intended to open the market more, but I think this move is as much motivated as being able to project economic power through Samsung as anything.