With email storage not being an issue in many companies (I think I currently have 25GB of storage on my email account, I don’t even think about storage), this encourages bad behaviors such as liberally attaching office documents to emails instead of sharing a link to the document in SharePoint or SkyDrive or some file share etc.

Attaching a file admittedly has its usage scenarios too, but it should not be the default. I thought I'd list the reasons why sharing a link can be better than attaching files directly.

In no particular order:

1. Better Review. It allows multiple recipients to review the file and their comments are aggregated into a single document. The alternative is everyone having to detach the document, add their comments, then send back to you, and then you have to collate. Wirth the alternative, you also potentially miss out on recipients reading comments from other recipients.
2. Always up to date. The attachment becomes a fork instead of an always up to date document. For example, you send the email on Thursday, I only open it on Tuesday: between those days you could have made updates that now I am missing because you decided to share a link instead of an attachment.
3. Better bookmarking. When I need to find that document you shared, you are forcing me to search through my email (I may not even be running outlook), instead of opening the link which I have bookmarked in my browser or my collection of links in my OneNote or from the recent/pinned links of the office app on my task bar, etc.
4. Can control access. If someone accidentally or naively forwards your link to someone outside your group/org who you’d prefer not to have access to it, the location of the document can be protected with specific access control.
5. Can add more recipients. If someone adds people to the email thread in outlook, your attachment doesn't get re-attached - instead, the person added is left without the attachment unless someone remembers to re-attach it. If it was a link, they are immediately caught up without further actions.
6. Enable Discovery. If you put it on a share, I may be able to discover other cool stuff that lives alongside that document.
7. Save on storage. So this doesn't apply to me given my opening statement, but if in your company you do have such limitations, attaching files eats up storage on all recipients accounts and will also get "lost" when those people archive email (and lose completely at some point if they follow the company retention policy).

Like I said, attachments do have their place, but they should be an explicit choice for explicit reasons rather than the default.