Earlier quoted context omitted.
They had a good blog post about this, which gave a good explanation. Basically it said that some huge percentage of FB app use was messsanger, so why not optimise for that use case instead?
Imagine a venn diagram, where the left circle is "FB users" and the right is "Messanger users". I think it's a quite big overlap. Are you seriously suggesting it was a right decision to degrade the service for the users using both services? That's not optimizing, it's just plain stupid. Nothing would have prevented them from both a) letting people do simple messaging inside the FB app, while at the same time b) provi…
And having the same functionality in two apps is not a good idea in any scenario.