Why is le needed here?

Hola Shirley

Tocar is an inverted verb, like gustar; it uses an indirect object pronoun (me, te, le, nos, os, les).

Here is a lesson on the use of "tocar" with an infinitive. It's not the same as in the example you mention but you can see by reading that lesson that it works in the same way using the indirect object pronouns. 

In a certain context, when we say that someone has won something like the lottery, or a prize, or when someone "gets" something by chance, we use the verb tocar - the person who is lucky and gets or wins something is expressed with that pronoun. For example:

I hope this clarified it.

Saludos

Inma