Because water evaporates (turning into steam) at a certain temperature.
Meaning it can't get hotter than that and still keep its liquid phase.
Once it turns into steam, it can get way hotter than water.
you are also giving the wrong answer
don't send such foolish answers
and also you
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While boiling water, it first boils then vapourises.
Therefore the vapour have extra energy called latent heat of vaporisation due to which it cause severe burn than a hot water 
you are an expert and why are u giving answers like this
please don't do like this
The reason steam has more heat, in the same amount of mass, is because water takes on additional heat to change from its liquid state into its gas state (i.e., into steam). That is, up to 100 C the heat raises the temperature of the water. But at 100 C, as the water changes to steam, more heat is added without changing the temperature. 
the more heat is called latent heat of vapourisation
i was just explaining in simple way