Beach farm bans the sprinkle. 1.6 adds 4 seeds in every season and mystery boxes can drop seeds. I think the author hope we plant many kinds of plants.
The beach farm is purposefully more challenging regarding the crops to incentivize changing your playstyle. You can still plant a ton of crops, but it will be harder to maintain.
You can always plant loads of different crops, generally people stick to one thing or another because it's more efficient on your time and effort (as well as crops being objectively better and worse than others), but nothing's stopping you from having a super diverse field with sampling from everywhere each season.