I build parts of my unfinished basement and do the work myself so it's done in stages. I am connecting several new circuits that should be active before all parts of the basement are completed. Without this type of connector I would have to remove the existing wire nuts to add new branches when I reach the next steps. Done right, this can involve disassembling the existing connection to properly add the new one back, which while acceptable from a code perspective is certainly more complicated and less convenient. With these connectors, it's almost like turning on a separate bus and just connecting new pins to these buses. Now you can add new branches one at a time without breaking the original connections. They're not cheap, especially compared to regular wire nuts, but it's hard to deny the speed and convenience, and using them in a gradual branch-adding situation like mine justifies their price.