People are dismissing this too easily. Looks matter, a lot. Tipping is an emotional connection - it's not a logical transaction. The tipper is making a contribution to something he likes. Giving 0.000000005 BTC gives the tipper and tippee an emotional message that his work isn't worth much. 100 DOGE makes it seem less petty. It's like giving a chocolate bar as a gift instead of $2 - you will get far more favorable reactions to the chocolate bar than a 'useless' $2.