Michael A. Terrell wrote:

Re-plant your seeds? How the hell do you do that? The seed becomes
the plant. The seeds from those plants are not the same as the seed
that grew them because they were grown from a hybrid seed. If you use
seeds from those plants you will not get the same quality from the next
generation. They revert to one of the varieties that comprised the
hybrid, all of which are smaller and less hardy.

Sometimes this hybrid issue is a natural result of trying to include
positive end-user charactersitics.

But sometimes it's an artifical issue introduced merely to prevent
replanting part of last year's harvest. Google "terminator gene"

And sometimes it's purely a legal "virtual property" issue - ie,
biologically possible to replant from the previous year's harvest, but
legally prohibited - and enforced typically be seed company inspectors
driving around checking unlicensed fields for plants with a proprietary
characteristic, such as herbicide resistance.