Because 900 people will then e-mail you digital copies of said show, or links to digital copies of said show, or offer to mail you CD/DVDs with copies of said show.
It really, really wasn't my intent to have everyone send me that last episode. Now that I know it's available at the iTunes store, I think I can swing the $2 to pay for it. But the lesson I learned is, Sheldon readers are pretty darn nice...and will respond with kindness at even a slight request for help.
So thank you for that! It's good to know that if a nerd is in need, fellow nerds will rise to the occassion.