Patents are a major PITA even in home gardening and small-scale nurseries. People have to respect the patents because a lot of plant sales are online these days, through Etsy and stuff, and the company will sue the ever living shit out of you if they find out you are selling them, especially on any meaningful scale.
Some of the best tomato seed varieties are often patented, e.g. F1 hybrid sungold tomatoes (though reproducing those is also annoying because they are a hybrid and people generally want seeds.) There are groups[0] which try to make varieties as heirlooms (i.e. collect-and-plant) seeds that are copyleft licensed[0].
For another interesting example of recent plant developments, Norfolk Plant Sciences developed purple tomatoes and recently began selling seeds of them. Unlike other purple tomatoes (of which there are only a few) these have purple meat inside, incorporating a gene from snapdragon flowers, which also keeps the tomatoes good longer. They are patented, $20 for just 10 seeds.
Another small company, Baker Creek’s “Purple Galaxy” tomatoes, has been suspected of re-selling Norfolk's purple tomato seeds and recently stopped selling them due to 'low stock' (suspected cease-and-desist) - as a minor controversy in the gardening community last week, though allegedly Baker's Creek is a white nationalist group so YMMV on whose side you want to take there.
Anyway, plants are fun!
[0] https://osseeds.org/