In order ot make LCD's of this type widely applicable, an industry convention has developed, which addresses the pinout as a standard. This allows mulitple competing manufacturers to operate in the same market. There are typically 14 pins in this de-facto standard, though there are two ways in which they're typically arranged, but the signal names are associated with the pin numbers, not their physical arrangement, in the two relevant cases.

No, there's no law that demands one use these pinouts, but it's worked for some 20+ years.

There are unconventional connectors used on some LCD's. Some have multiple HD44780's, hence, require more than one 'E' strobe. Some require a backlight supply that's integrated into the connector. Even those tend to use the first 14 pins in the conventional way. There are exceptions. That's why it's vital that one have the datasheet for the precise LCD module that one's using.

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