The hub was created by the "Final Five", although the Cylons know how to use and operate the technology they lacked the knowledge to replicate the technology. Seeing The Final Five lost their memories they would be unable to help (and probably unwilling as well) build a new one.
The technology was original created by the Original AI's on Earth, but after they eventually started to reproduce naturally the technology became obsolete and lost. But the five were researching a re-invention of the technology. Eventually it was this that spared them from the Holocaust that happened on the original earth, seeing they got resurrected.
Each one of them knew only a part of the entire process so all 5 of them would be essential in recreating the technology (it would probably be possible with fewer, yet each member lost would significantly increase the required research period).
The Five offer to give back Resurrection if they agree to leave humanity alone forever. They combine the keys to Resurrection technology in their minds and start transmitting to the Colony, but a side-effect is that they see each other's memories at the same time. This leads to a conflict between them about past actions , breaking the Five's download to the Colony and killing one of them.
Later, the people of the Fleet have one of the five fly Galactica and the other ships into the Sun, destroying the ships and himself. With the deaths of these 2 out of 5, there are only three of the Final Five left alive making it near impossible to replicate the technology.
The most inportant scene that shows this is the one where they strike a deal with Cylon #1 here. It is clear from this scene alone that the Cylons needed help from the Five to rebuild the technology, something they were willing to give in exchange for peace. (This happens during the final moments of the Cylon/human conflict where Cylon #1 takes a hostage on the Galactica bridge.)
Source episodes about the 5 being the ones that build the resurrection hub: "No Exit", "Daybreak, Part I", "Daybreak, Part II"