There is definitely a snowball effect though. Once I signed up for Gittip people started to give me tiny amounts (like $0.25/week). It built up-and-up over time and now I'm getting a non-trivial amount of money per week, which is awesome! It's helping to pay for all of my hosting costs and then some.
It's very defeatist to give up before even trying ("only" a cup of coffee). Why not aspire to more?
I'm happy that you're finding personal benefit from Gittip. If it allows or helps you to keep providing great work to the community, that's excellent for everyone.
However, the numbers you quote are not good. $13 is an amount that a Bangladeshi garment worker earns in a week or so. It's nobody's aspirational goal to earn that in a year.
It may be the case (in the wider population) that such disproportionately small rewards actually discourage contributions compared to volunteerism, as it provides a (very bad) point of reference to compare the value of open source work to paid commercial work.
The old reality (people giving money to Open Source projects /developers sporadically) was bad. The new reality (consistently giving small amounts of money via Gittip) is better. The future (large amounts of money, equivalent to a paid job, in a consistent manner) will be even better. I'm pushing Gittip because I see it as the best way to bring that future about. It'll take a lot of work but it needs to happen - for the benefit of all Open Source developers.
Chad's goals for Gittip are much larger than paying people to write code. But all big ideas start somewhere. I'm an eternal pessimist and I can say that Chad is on to something really big with Gittip. Not sure anyone knows exactly what it is yet though.
1) When a famous developer accepts tips despite the fact that they don't need them, and then regifts them to "unknown" developers that are known to them, perhaps as the people behind the scenes on the projects they're famous for.
2) When you set up an (opaque) project account such as ReadTheDocs has done: https://www.gittip.com/readthedocs/. ReadTheDocs can split that under the hood however they want.
3) When you set up a (transparent) team account and everyone on the team gets to take some of the money given to the team. This is a relatively new feature, see: https://medium.com/building-gittip/eba0a27825b8.
Again, though, funding will always grow slowly. Gittip is for the long term.