They only do it when the word after the 'ah' word begins with another vowel. For example, "I like drama and comedy" will be pronounced like, "I like dramar and comedy."
It's to space out the two consecutive vowels and keep them distinct. In American english we end up saying something like "I like dramund comedy" and slur the two vowels together.
This comment was edited on Sep 18, 08:53.