If they have stopped working today it would be disaster. If it stopped at that time, life would go on. It is not about technology but how society adapted around it.

"Disaster" is a very subjective term. One man's disaster is another's normality.

How many people died between 1812 and 1815 because there were no Trans-Atlantic telephone lines? About 30 thousand soldiers, wasn't it? Probably quite a few civilians as well.

I'd call the preventable death of 30 thousand men a disaster, wouldn't you? But in 1812 it was business as usual.

Would you say penicillin isn't essential, just because it's 1928 and people are accustomed to deaths from bacterial infections?