This may not be a problem for users no high speed Internet connections, but if your Internet is unreliable or slow, you may not want to go through the whole ordeal again especially since there is a chance that the operation may stop again at one point in time. When you start it, the process will resume the last operation instead of starting completely anew. This means that it will resume the creation of the media using the downloaded setup files. Since the download has a size of several Gigabytes, it can happen that it stops at one point during operation, or that the operation stops at the processing phase. Steam is constantly implementing new steps and security measures to keep on top of account stealing, manipulation of secure information, and or theft of that information. No workaround or alternative is available right now that would improve the experience for users.