They don't make consumer level desktop boards with dual/quad sockets because consumers don't need them. They make workstation & server boards for that purpose, because servers & workstations may need multiple cpus.
MS doesn't make 'Home' OS's that work with quad sockets (dual sockets is OK for most of their OS's), because they aren't needed either. If you need quad sockets, you are not really a 'home' user - and need to buy the hardware that goes with it.
Similarly Intel/AMD don't make multi-socket capable chips for home use - because home users don't need them. See the pattern emerging? You get what you pay for - you need multi sockets, you have to buy the hardware/software that will support it. If all the features are available on all the hardware, the price of everything has to go up as there is nothing to differentiate the top hardware from the lower grade stuff.