Indeed. If iPod touches had cellular radios in them, I wouldn't need an iPhone — but then they'd probably also cost the same, so I'd just get an iPhone anyway.
The iPod touches also have lower-quality displays, lower-capacity batteries, base units have less storage capacity, usually have older or slightly underpowered A chips, and lower-quality materials leading to a slightly inferior build quality compared to iPhone.
(Also, iPod touch hasn't been updated for three years)
