There wasn't a need for it VIII's story line... Maybe they don't need them. Probably if you play the game you might catch someone using one.
It's...a rather major part of early plot that there is no wireless communications.
Different advances in technology. In FF6 there were giant magic-powered machines but no cars. In FF7 there are mako reactors but no flying cars. In FF8 there are flying cars but no cellphones. That, or the satilite with Adel jams cellphone signals too.
For the same reason Aeris died from a cut nowhere near vital organs...it' s the plot, it's planned don't argue with it.
More to the point, why do there need to be cellphones? The game's about saving humanity from an ancient Sorceress, not texting Irvine about dinner or uploading your twitter page.
It's explicitly stated that wireless communications haven't been possible for nearly two decades (due to Adel's prison in space). Look up Radio Interference in the wiki for more information.
The person who said the Aeris thing, I wish there was a "like" button for that. I've been bothered by that for a long time now. (Especially the Aeris v.s. Aerith. It's freeking Aeris!)