The seedless grape technically has a seed, but the seed has no hard outer shell and is microscopic/invisible. These seeds aren't viable. Technically you could isolate out the seed tissue from the grape and grow it in specialized germination medium, but that process also works for any other part of the grape plant. Hooray cuttings! Certainly the seedless grape would not grow if you put it in the ground.
The fruit part of the seeded grape is 'bait' to get animals to ingest the grape and carry the seeds within inside their digestive tracts. The goal is distance, but the surrounding feces provides bonus nutrients. The fruit is not designed to feed the seedling grape, but instead to act as bait for herbivores. The grape is mostly sugars and water, which makes them excellent bait but not amazing plant food. Plants can make sugar from the sun and pull water from the ground, but nitrogen and phosphorus are harder to come by.
Contrast fruit (which are for animals) with coconuts, which are examples of large fruit storing lots of calories for the seedling itself. The coconut flesh isn't as sweet as fruit, and it's much harder to get at.