Why do guides always say to download the RPM to disk?

Question

Every installation guide I've ever seen which requires an RPM install starts with the instruction "download the repo", usually accompanied by a wget, and then, separately, says to rpm -i or rpm -U the downloaded file.

Except I've noticed rpm supports remote URI schemes (at least, it supports FTP, HTTP and HTTPS). Clearly, to install a remote repo, rpm must already download the file (maybe not to disk, but I'd be surprised if it didn't). So, presumably, the issue isn't that rpm can't just install the thing given a link.

My Question

Besides the utility of having an audit trail, the convenience that comes with being able to do the install offline, and the fact that a failure on install wouldn't require a redownload of the RPM, are there any good reasons to install from the local drive? Does rpm treat local files differently?

-- Also, just in case anyone happens to know --

If the files are downloaded to disk (which, again, would be the overwhelmingly sanest thing to do), are they removed at program termination, or do they persist? And if they do persist... where?

Answer 1

Downloading rpm file first can be a huge time saver, not for mere installation, but for inspection of rpm package before installing. People can check out what they are trying to install (rpm -qlpv, rpm -qp --scripts and so on), if the rpm is compatible with distro (rpm -qpi), etc. The whole file will need to be fetched over and over if the direct URL link is used.