A 035 Follow-Up

Yes, that's correct. Having removed the 3.0 Ambidexterity feat and incorporated that benefit into Two-Weapon Fighting, every D&D character is effectively ambidexterous.

A 036 Follow-Up

There could be any number of reasons, including style. A mechanical reason in addition to weight would be a DEX bonus of more than +6: the chain shirt would limit that but Bracers of Armor or a similar armor-enhanced robe would not. This isn't really a "simple" question any more.