Most of the devs I know have a habit: They must do something every day 
Payment protocol stuff was a business demanded feature, intended to address some of the problems that have cropped up with Bitcoin URLs. Its certainly not something sexy or exciting to work on.If it were business demand then there would be a business case and a solution for it.
Where do you think Gavin's salary comes from?
There is a strong business case, he's coming up with a decent solution for it, and because his paycheck comes from the foundation rather than a specific company he can come up with a solution that can be used by everyone in the community and doesn't privilege any particular player. (except certificate authorities, initially, but the payment protocol is pluggable and more decentralized PKI systems can be easily added later as they are developed)