Mobile phone locks that don't lock

Why are mobile phone key locks so rubbish. Every phone I've had has had a problem with the key lock not actually locking the keys.

My latest one (Vodafone V1240) unlocks the keys when the phone rings, when a reminder pops up or when you get a text. I now regularly answer the phone by accident in my pocket.

My last phone (O2 XDA IIs) didn't lock the phone buttons for the camera and things on the side so I had to download an aftermarket screenlock (called ScreenLock!) but that was temperamental and I couldn't always unlock it in time to answer calls!

The one before that (Sony Ericsson P800) used to lock all the buttons except "9" and "Dial" so once a month I found that I had called the police. I downloaded a different screen lock for that one which worked for me.

The one before that was ok - I think it was a Panasonic with a sliding switch for the lock, ditto my original Motorola flip phone which didn't do anything with the flip closed.

Another great example of technology going backwards over time.