.VA is a country code TLD, assigned because it is listed in ISO-3166. The others are "generic top-level domains" which had to go through ICANN's new gTLD program, which has a lot of rules (338 pages of them for the 2012 round) and costs a lot of money (US$185K to start with recurrent fees dependent upon the number of registrations). I suspect it isn't about centralization, but rather about perceived cost/benefit ratios.