The main reason is because it's in active development by the open source community.

So IBM wants to take the code and use it for commercial offerings. If you don't believe that, look at IBM's Lotus Symphony, which is a (crappily) re-branded OpenOffice with a few user interface tweaks and bugs fixed. Being a massive backer of Apache OO, IBM does not want to lose the ability to leech back improvements into Symphony (which I should add is a commerical product they support).

As a result, IBM is willing to keep Apache OO alive. LibreOffice has already massively pulled ahead in features and bugs fixed / shit code re-factored. It is just the name that keeps OO alive in my not so humble opinion. Either way, Michael Meeks and the (former go-oo) team that now work on LibreOffice will continue kicking it. In OSS, forking isn't always necessarily a bad thing. Choices keep both sides honest!