No, sentences like 'She left home as she had to buy some bread ' aren't normal in everyday speech. I'd ignore this advice and stick with 'because' if I were you.

Well, It is used, but it's wrong according to grammar to use "as" when u want to give an explanation.And Mostly "because" is used in daily speaking. Ex:I came late, cuase I took the subway. or because*

Because :for the reason that; since. As: used to indicate that something happens during the time when something is taking place. Very agreeable with Alexey Lekomcev if you have checked out English dictionary.

As is used then two events happen at the same time. For example, I met him as he out of the bus. In this case 'as' is does not mean 'because'.