They know exactly what they're doing
If they really believed it was as simple as "Look guys, just give us access so we can stop the terrorists", they wouldn't go to the trouble of issuing communique's with veiled threats of legislation for non-compliance - they'd just jump directly to legislation. They know exactly what they're doing and they don't want a backdoor. They want a culture shift so that encrypted messaging goes away completely, so that the very presence of encryption is a cause for interest.
All these stories about tech companies refusing to help isn't aimed at you - it's aimed at the man on the Clapham omnibus. They want him to ask why Whatsapp messages use end-to-end encryption in the first place - why this is a concern now when a couple of years ago he could just send an SMS and it worked exactly the same but didn't help the terrorists and pedophiles. They want broad consumer support in place before they legislate against the use of end-to-end encryption in consumer messaging products.
They know they'll never stop encryption - that's not the goal. They just want it so that nothing on the app stores use end to end encryption, so anybody left who does still use it becomes interesting again.