Actually, it doesn't work Most LCDs require not only ASCII text data, but special control signals as well. Simply sending raw ASCII won't make it show up on the character LCD module. First there is an initialization sequence and then each character needs to be clocked into the LCD's internal RAM.
It wouldn't be hard to write a program to pipe text to it that you could use in a batch file... I have a simple C program for DOS that lets you type characters and have them show up, like a word processor.
Serial LCDs have all the "brains" needed to convert serial ASCII into control & data signals to talk to the LCD properly, and DOS knows how to send standard serial data, so that is why you can pipe text into a serial LCD so easily.