Only one single server box needs to be protected against virus attack. This saves millions of dollars for the company by avoiding installation of vaccines and cleaning the hard disks. Fault tolerance of hard disk failure is possible by using RAID on main server. Very few system administrators required to maintain central server. Zero administration at diskless client side.
Diskless computers are absolutely maintenance free and troublefree.
Long life of diskless clients. Can operate in places like factory floor where a hard disk might be too fragile. Another solution is to use a device which will load a local kernel, which will mount the root filesystem on the server. On the other side, if application programs are really executed locally on the stations, the requirements for the stations depend completely on these applications. In that case, only a small server is required.