It's just an example, i have read sentence like it several times.
THE "ing" form of the Verb is used to express or do ( doing/ action ) words.
a concrete action comon in spoken & writing Language that expresses or describing the action
is taking place "now " called present tense.
It's because of the preposition 'for'.
I can give you a very simple rule here: With the exception of 'to', the verb which follows all prepositions is always in the gerund form.
If you write a verb after a preposition you should use +ing, except with infinitives (to be, to read, to speak...).In these cases, it's not necessary.