The Philippines has long-standing territorial claims over Sabah, but it has not been able to annex the territory due to several reasons:

1. International law and agreements - Sabah has been part of Malaysia since 1963, when Malaysia gained independence from Britain. The Philippine government's claim to Sabah is based on historical ties, but it is not recognized by international law and agreements. The Malaysian government also considers Sabah as an integral part of their country, and any attempt to annex it could be seen as a violation of their sovereignty.
2. Political and economic implications - Any attempt by the Philippine government to annex Sabah could result in a diplomatic crisis with Malaysia and potentially other neighboring countries. It could also have negative economic consequences for both countries, particularly in the areas of trade and investment.
3. Military capabilities - Annexing Sabah would likely require military force, which the Philippine government may not have the capabilities to do. Any military action would also likely face strong opposition from Malaysia and potentially other countries. I mean the British had a military agreement wuth Malaysia to provide military force in case of Malaysia under attack
4. Domestic politics - Annexing Sabah is a sensitive issue in the Philippines and could be politically divisive. The Philippine government would need to carefully consider the potential domestic consequences of any attempt to annex Sabah.

Overall, the territorial dispute over Sabah is a complex issue with political, legal, economic, and security implications. While the Philippine government may have historical and demographic ties to Sabah, any attempt to annex it would likely face significant challenges and potential consequences.