Why did Tom say "Blow out you candles laura for nowadays the world is lit by lightning"?

The end of the play is very interesting. I think light is a symbol of hope,but why should laura blow out her candles since her hope "Jim" was gone maybe it is to say Goodbye to the audiance but it still confusing blowing out the candles just because the world is lit. what is the relashionship between the candle and the light found in the world