Why don't planets made of explosive gases like methane ignite?

Methane is NOT easy to ignite. Contrary to belief, it is hard to ignite, while hydrogen and helium are not. Also, even if methane was explosive, the only planets with significant amounts of methane are Ur, and Neptune. These are too far from the Sun to receive enough heat to generate a planetwide explosion even if they were made mostly of hydrogen. For example, the new rocket engine fueled by methan was MUCH harder to ignite than the liquid hydrogen oxygen ones currently used.