Because part of the concept of R&D, last I was aware, is that you won't know exactly what you're working on until you finish. If people know what's on the R&D list, then they'll be more likely to figure out what they need to research next to get to their intended goal.
"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."
Most recent plans were a tech tree style, where you needed to R&D each step to move upwards. Some entities would be restricted to the first X people or whatever, others would be for everyone.
Beyond that, how to R&D and progress has a couple of different paths that are being thought of.
As for the lists being publically available, as Hal said its to prevent people from trying to plan far ahead etc. However it will follow canon progression as much as can be decided at least (ie YT-1210 -> YT-1300, etc) so in that regard you can guess and work from that. I've been working on a ship tree for Sin, but he plans on getting Jesfa to link groups of ships that aren't canonly linked so players like me don't know how to get there (ie going from a Hapan Battledragon to a stardestroyer, there is no real canon link so one will have to be added somewhere - that will be up to the devs to decide where to place it).