https://s3.amazonaws.com/s3.documentcloud.org/documents/8858...
https://s3.amazonaws.com/s3.documentcloud.org/documents/8858...
[0] http://www.cbc.ca/news/canada/nova-scotia/emc-wins-contract-...
And there may be some huge PDFs (think 100Mbs) that you might not want to download, just check some pages.
At some point "convenience" becomes annoyance. Because instead of encouraging people to do the sensible thing like breaking documents into smaller, digestible pieces (e.g. small PDFs, page images, etc.), they are encouraged to be lazy (e.g. throw a 500 page document in a scanner that outputs PDF, and upload the oversized result to one of these annoying sites). Then the average user tries to access it and she has to wait patiently while the browser tries to load this ridiculously large file, or her browser just chokes. So, "time saved" on the front end - easy scanning of docs to PDF - can often lead to "time spent" dealing with the mess on the receiving end. The uploader gets convenience, the user gets annoyance.
That being said (1) the link you posted is not posted within an embedded context, so there's no benefit as you described, as far as I can tell; and (2) I can't zoom in properly since it's using GIFs, which is really annoying because now I have to click a link, visit it and wait for it to load just so that I can click the .PDF link -- I'd rather click a PDF link to begin with.
There is a certain very valid and extremely useful use case to sites like this, of course, linking random internet users to pdfs through them shouldn't be one of them ;)
I am in no way affiliated with any of these services, just came across this use case while building something for someone in the past.
I see little value in taking a PDF and making it available as images online. Is there really a web browser that cannot display a PDF?