That's because you have the right to travel freely between Schengen countries.
Asking for an ID or passport when embarking/disembarking would be similar to having an ID check at a border, and would therefore be a border control, i.e. no longer free travel.
Of course Schengen countries have the right to temporarily re-enable border checks.
Asking for an ID or passport when embarking/disembarking would be similar to having an ID check at a border, and would therefore be a border control, i.e. no longer free travel.
Of course Schengen countries have the right to temporarily re-enable border checks.