It's what happens, it's almost by definition not subjective. The world is full of people geeky enough to use third party clients but not geeky enough to understand the nuances of service evolution. Their reasoning goes like this: yesterday it worked, today it doesn't. I didn't change my client, so it must have been the service that changed. Therefore, it's the service's fault.

This type of reasoning is typically reinforced by the third party app developers themselves, who will tweet "XXX broke their APIs today, really sorry, working hard to get you an update that works around their $@!%#! engineering" and other stuff that not-so-subtly encourages people to blame the service.

Also, don't discount the abuse aspect. Closing clients and out-iterating them is a proven strategy for winning the abuse war, and as all users care about abuse but very few care about third party clients, losing the latter to please the rest of the user base is an easy decision to make.