Because the batteries and charging equipment in them explode into flames far more often than stuff regulated in north America or Europe.
Far too many people have died due to cheap Chinese electric bikes starting fires in their homes.
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Gonna be real here, I'm in tech, there is no fucking way I'm gonna open my PC to the entire fucking internet. Vulnerabilities are everywhere and no code is perfect. Firewalls and nat help stop so many attacks from the start.
Even if ipv6 is common I will assume most implementations will be nat based.