You've seen birds out on a new lawn just after seeding, pecking at the grass seed. Next, Jesus notes that some seed fell on rock. This wasn't plain rock, but slabs of limestone in certain parts of the field just under the surface with an inch or two of soil over them. Since they couldn't get a root down into deep soil, they would quickly wither and die. Now this makes perfect sense to a California boy like me who grew up in a Mediterranean climate similar to the Holy Land.
Rains come in the fall and winter, as much rain as there is, anyway.
Late spring and summer see little or no rain. By May the green hills of spring are turning brown as the grass dries up. If you are from a region where it rains all summer, withering and dying may not be part of your experience. But in Palestine, seeds had to be sown in good soil if they had a hope of making it to maturity. In your mind's eye you can see the plant growing vigorously only to wither and die when the rains stop.