Very Quick - perhaps you should look into MOP (and the philippines in general) a little deeper?
The political climate in 1970 and infact until fairly recently was not exactly favourable for anyone wanting to mine the proven resources of the philippines...
times have changed though and the government is now actively encouraging outside investment and you will see from the extensive activity by many mining co's in the philippines that there is much to be gained from the area.
So in answer to your question, no - they would not do better putting their energy into other matters...