Soaking seeds before planting or sowing those seeds is not necessary but the benefit of soaking the seeds before you sow them is that the germination time for the seeds is reduced.
So when you soak the seeds for 24 hours before sowing or planting them the seeds will produce the plant much sooner than it would without soaking the seeds.
Just avoid soaking the seeds for too longer otherwise it will damage the seeds and then they won't germinate at all.
You can soak the seeds in water for 24 to 48 hours but no longer than 48 hours.