Why get a desktop computer over a laptop?
Laptops are very convenient when on the move and for people who need immediate access to a computer. Laptops, however, need to be charged or near somewhere where they can be charged, generate a lot of heat, and are not always the most efficient with their hardware due to miniaturization.
Desktop computers provide a stable work environment, can be used for such things as hosting servers and files for your laptop while you are on the go, and are, typically, far more powerful for the money being invested in them. Additionally, desktops can be upgraded, extending their usability through several generations of hardware and software, rather than needing to replace an entire costly laptop system.