Why would a civilization choose to inhabit a single enormous vessel instead of maintaining interstellar colonies?

They have the destination, they heading to┬áSupermassive black hole. reasons are┬áTLTR, if short it allows to overcome some growth problems for a more extended period of time and have a bigger population as result. At the moment, this is the only place I know, where is possible to extract energy more efficiently than with any … More Why would a civilization choose to inhabit a single enormous vessel instead of maintaining interstellar colonies?