Why do RAM sticks need to be separated in the DIMM slots?

Memory DIMM slot install order slot dimm It's not the only example of a desktop motherboard with SO-DIMM slots Asus cooked one up in its labs, and it was spotted by wxnod at XTwitter, slot rtp 666 Dual In line Memory Module : The DIMM slots were introduced to cater for multitasking in computing devices

slot machinecom A server provides 16 DDR4 DIMM slots Each processor supports eight memory channels and each memory channel supports two DDR4 DIMMs Figure 2-14