Indirectly, this excellent presentation on Google Drive and how to use it actually makes the case for continued use of e-mail attachments as a superior method of transferring smaller files.
1) No training is required to use e-mail attachments.
2) Attaching is quicker than uploading then sending a link.
3) The recipient does not need a Google Drive account.
4) Attached files are less exposed to snooping.
5) There is no conversion from Microsoft Office formats.

Google Drive is good and is useful for sharing large files and for certain collaborative tasks, but it is inefficient and perhaps undesirable for other tasks. Use it when it is the correct tool, not because it is a new tool on the block.