Why is it unlikely to find pure alkali metals in nature?

 High Reactivity

Explanation:  Alkali metals are the metals which are kept in the group 1 which is also known as S -Block elements.

The electronic configuration of the elements can be written as ns1 .

These are considered to be the most reactive elements of the whole periodic table because their outermost shell has only 1 vacant electron and thus are in need of only 1 electron to complete its duplet or either they can also lose that  one electron .

This the reason they can never be found pure in the nature .