One other reason is that Nigeria has a fast growing Bitcoin market, with a large percentage of the citizens looking to understand and own Bitcoin. Bitcointalk being the largest discussion forum for Bitcoin would attract a lot of these users as we can see by checking the activity on the local thread. Having a dedicated local board would make those users feel more welcome and create a strong community.

I noticed that some of the arguments against the Nigerian board in the past, was the lack of a distinct language;
• Pidgin English is a very distinct language in Nigeria and parts of Africa and is common to everyone irrespective of tribe.
• Local boards aren't really divided by language, but rather it's a community of individuals who share things in common.
• On a micro level, there are news and updates that would be useful to the Nigerian community, but not so to the rest of the world. Having a board to post such is a welcome development in my opinion.