Because Stoot said so.
Just to torture you.
I, personally, think we should be able to make tomatoes from cherries, but that is a whole different debate.
Actually, I think there's another reason for this, and it involves a quest. I vaguely remember a quest telling me to buy strawberries from the produce vendor, or to change them, or grow them. I could be wrong, though.
Technically strawberry plants are more closely related to Herbs then vegetables due to the lack of woody or hardy stock (stem). So really the mystery deepens...
Boaz
Technically bananas are closer to herbs than fruit, but we can't grow them in herb gardens... tomatoes are technically a fruit but are classed with the other veggies in game, and so are strawberries (except when we can make them from a fruit-changer!)... but this is Glitch after all :)
Well, tomatoes, strawberries, cucumbers, and zucchinis, and PUMPKINS are all fruit, since the part that gets harvested contains seeds. So we should technically be able to make those with a fruit changer too.
Well TECHNICALLY, strawberries are a variety of fruit, bananas are classified as dairy products, cucumbers are a kind of meat, pumpkins are mammals, tomatoes are gambling devices and zucchini are specialty Volkswagen parts.
And TECHNICALLY, I am a fire truck. WEEEOOOOEEEEOOOEEEOOOO!!
I talked myself blue trying to explain that same point when people were arguing back and forth about the resources that foxes, sloths, monkeys, etc. could logically provide.
As if real-world logic matters in Ur!
(And it seems dm agrees with us, although far more eloquently!)