Why do dry polyspermous fruits open?

Since dry polysperms do not have juicy pulp, they are forced to open (that is, to open their fruit). They do this so that the seeds get into the soil, where there are many nutrients, and there is constant moisture (moisture is not always in the soil). And in fruits that have pulp, it is already full of moisture and nutrients, and the seed is comfortable to develop in the fruit. (But before the right time and in a juicy fruit, the seed will fall into the soil.)