It's just 3 phases with 230V each, which gives you 400V across individual phases. Same safety rules apply as on standard outlets, so yes, it really is just familiarity. Also lots of European households do have 400V outlets (we have 2 in our house, basement and garage). I even installed one temporarily in my living room for construction/remodeling and working with the required thick wires they are unconfortable to work with.