Yes, they were engineered that way, but why? Is it because hybrid tomato plants fruit all ripen in a fairly short period of time? Because if only the blooms on the main trunk were available to fruit, one wouldn't have nearly as many tomatoes would one? So why would one even think about pruning suckers?
They only do that if you don't prune.
If you prune suckers, the plant puts some of the saved energy into earlier production of tomatoes, & some into larger, better quality tomatoes.
If you have three/four/five single-stem tomato plants in the same area as one unpruned plant, you have three/four/five root systems taking up nutrients & water instead of one.
If you have three/four/five single-stem plants in the same area as one unpruned plant, & you notice early signs of disease, you may be lucky & lose only some of your plants, whereas, with one unpruned plant you lose the lot.
Also, in unpruned tomatoes, the inner fruit get much less light, making them much lower quality.
In the US you have much better light than we in the UK, so if your unpruned tomatoes need 3'x3', we, in the UK, who need to leave 18" between plants, can get four in the same space, whilst, in general, you yanks can grow NINE a foot apart.
You will never convince me that you get nine times as many tomatoes from an un-pruned plant.
Furthermore, the extension of the season is backwards, as in starting earlier, so those weeks when you're desperate for a home-grown tomato, having had more than enough of the poor, crisp, tasteless balls of water, that supermarkets call tomatoes, are fewer.
It is, of course, far more work
