What is the actual reason for directly investing in US ETFs like QQQ, SPY, and VOO?

With direct investing, you can't even trade properly because of taxes, whereas
if you invest in domestic-listed replication ETFs like TIGER or KODEX through retirement pension + ISA accounts (up to 38 million KRW per year),
the taxes are deferred and aggregated, and even if you withdraw the money early,
the taxes are lower than direct investing..