[mongol]

And I wonder what was the constraint to not make it longer when they developed the standard. Making it a few digits more seem it wouldn't cost much.

[omcnoe]

The cost will be in updating every legacy postal system that currently has fixed column lengths/input field length limits.

[topsecret]

Yes, now, but the person you're replying to was asking about at inception.

[rjh29]

Why was IPv4 so pitifully small? I guess most people thought 100 million parcels a year was a ridiculously generous limit that we'd never reach.