Why are the majority of characters named after car manufacturers? Most of the character's last name comes from a car manufacturer. Acura is a luxury car manufacturer under Honda. Gaz is a Russian car manufacturer. There are others like this such as Trabant, Lancia, Arbath, Dodge, Calloway, etc.

Has the author given his reason for this naming convention?
Sakaki Ichiro (aka the author) used a distinctive naming scheme in his other work Scrapped Princess as well, but there the characters were named after firearms / guns instead (its wiki page even has a section about that).

So it may very well just be that he likes to have his character names be a reference to something. :)