Can lay people acheive enlighment (Arahanthship) in this life by adhering to Buddhist principles?

During the time of Buddha, it is said many people at one gathering attained enlightenment by listening to only one one of his sermons. How can a mind develop such a achieving within matter of hours. There are millions of devoted Buddhist in the world now but I have not heard a single person achieving higher mental status. Are there any other explanation this other than karma?