Why would someone start to voluntarily pay for content that had previously been free, especially when they can continue getting it for free (by not signing up f

Why would someone start to voluntarily pay for content that had previously been free, especially when they can continue getting it for free (by not signing up for flattr in the first place)? I can see some people using this, but I know high school me would be saving up my money for a new computer, not paying pennies to content providers. Even now, I might throw $20 in to try the service but there are other things I'd rather spend that money on (like a monthly iPad 3G plan or drinks with my friends).