My parents got one around when I went to university. It was a really good fit for them and helped us keep in touch. Main benefits:
* It did its job - a light showed up when you had something to read, otherwise you don't. * Always-on, no boot time. * It fit on the kitchen worktop, whereas PCs took up a lot of space. * The predictable schedule of dialing up, retrieving e-mail and then disconnecting let them know what their costs would be, even if they were a bit higher than the (variable) costs of normal PC internet use. * It had good contacts storage (with dockable electronic address book you could take away), at a time when you would still expect to be managing a list of telephone numbers on a piece of paper.
All for less than a PC. They could have got all the same things out of the PC, the Em@iler just put it in more convenient package.