Each person may be a pro, but time spent in meetings and hallways costs money. Sometimes just trying to schedule a meeting can delay a project by a week or more. Spare parts such as cables and hubs and switch ports, if available at install time, can be the difference between an installation that proceeds and an installation that stalls. A lack of communication with the project owner or users can cause a reinstall, and frustration for everyone. Politics, the desire to simplify, poor past choices, fear of the unknown, and familiarity with old technologies are all among them.
Disk space is eaten up, CPU cycles disappear, and network traffic increases.
Failure to keep this in mind while implementing a new system results in one that is soon overworked, and thus tricky to maintain. On the other hand, the best solution is sometimes rejected because it's too complex, so a simpler one is implemented, even though it does not adequately solve the problem or lacks needed flexibility. There are also commercial tools that solve most problems. The result is a problem that remains unsolved. The antidote for system administration fires is finding their causes and sources, then solving them.