Why do some masajid ask us to read Surah Fatiha in dua?

After Farz prayers, normally the Imam does a dua in which we all participate. I have observed a few masjids I visited, the Imams in middle of dua say 'Al-Fatiha' and then goes quite for 20-30 seconds (I assume he is reciting Surah Fatiha). What is the significance of this? Is there a Hadith I can refer to understand the context?