Watermelons are not true to seed- a watermelon grown from a collected seed will not necessarily resemble it's parent. But surprise melons are fun! Usually not as sweet as those with carefully controlled genetics though.

It's all about profits. Seedless watermelons usually sell better with American consumers.

In order to produce fruit on triploid watermelons there has to be regular seeded (diploid) varieties in the field. Traditionally they would use a large oblong traditional seeded (allsweet types). Mainly because there was a market for them and they looked different than the seedless varieties.

The growers had to dedicate 1/5th of their acres to growing a seeded melons which they could sell at 50% or less than seedless varieties.

That's when seed companies introduced dedicated pollinators (non-harvested). These untilized several different dwarf genes and could be interplanted with seedless varities with no loss of space.

With the exception of the big party markets like the 4th of July, most fields utilize the dedicated pollinators in the U.S. now. For production in Latin America, they export the seedless ones to the U.S. and sell the seeded ones l ones domestically.

Bottom line, today you only occasionally seeded watermelons in grocery stores in the U.S. and Canada.

Nah, they don't really care about gardeners. They need farmers to buy new seeds every year.