select distinct point?

You can't select distinct on the point datatype column? I see why it's
nonobvious how to sort points but then how come it works fine to select
distinct on a box column?

slo=> create table test (p point);
CREATE TABLE
slo=> select distinct * from test;
ERROR: Unable to identify an ordering operator '<' for type 'point'
Use an explicit ordering operator or modify the query
slo=> create table test2 (b box);
CREATE TABLE
slo=> select distinct * from test2;
b
---
(0 rows)

--
greg