The source is freely available, so if there is a need to fix something, it can be done without external assistance. It's also much easier to debug. Linux has message and error logs to indicate specific problems, and if that doesn't work, one can always read the core files. It comes with networking built in, so there is no need for third-party software. Compilers and development libraries already exist, so there is no need to buy expensive libraries.
Drivers evolve quickly since many people worldwide are working in Linux to develop software.
Many commercially available UNIX systems don't have the driver support, due mostly to a limited staff. Often, one has to buy extra driver packs. With Linux, most drivers are free. In addition, Linux does not install a new package or replace system libraries without letting users know. Window programs often store things in the main system directories when a new program is installed.