I think Facebook is vastly overestimating the number of people who are actually going to go out and "like" stuff.
And I'd SWAG that an order of magnitude more people are capable of Liking than are even able to create a new link.
It took me approximately 90 seconds to implement from looking at the docs to deploy to one of my sites.
Also, often like buttons are used on something like stories, so you're only adding the code to one template, and now you have tons of like buttons all over.
I did the same thing that you did, wrapped it all in a like_url helper.