Two words - "base load". In developing economies, sufficient base load power doesn't exist. Solar and Wind do nothing at scale when a stable base load power supply doesn't exist.

SolarCity is experimenting with batteries powered by intermittent power supply in small islands but nothing at scale really exists a practical proven tech.

Natural gas requires high security LNG terminal infra if you're not a producer

I imagine it's much harder to quickly prop up solar generation than it's to build a few coal plants.

You would need some backbone before you can add solar on top (e.g. what happens at night?)