Tomatoes are an inoffensive filler vegetable. You might slap a couple of slices on your burger or mix it into your pasta sauce with enough sugar and herbs to make it edible, but you'd call someone a freak if you saw them take a bite out of a tomato like they mistook it for an apple. But tomatoes used to taste quite good, once upon a time. Around 70 years ago, the common tomato was sweeter, more aromatic, and generally more flavorful.
So what happened? Put simply, farmers noticed that tomatoes sold better the redder they were, because buyers figured that meant they were ripe. So farmers began to deliberately breed tomatoes to be a uniform red. Of course, most tomato buyers aren't biologists, so they didn't know that the gene that's responsible for holding back the redness of a ripening tomato is also the one that gives it flavor. If you remember the basics of high school biology, you know that the green parts of plants contain the mechanisms (chloroplasts) which turn sunlight into sugars. Deprive a tomato of those, and you wind up with the balloon full of bland pulp that we have today.
Not even this perfectly-lit stock photo can make them look appetizing.