Song form developed over many years to what it is today. In another 100 years there will probably be new standards to song form that we wouldn’t consider normal today. That’s how change happens.
Early American songs were often either strophic, 32-bar form, or verse-chorus form. Strophic songs are a single repeated verse and lack a contrasting B section. 32-bar form and verse-chorus form both feature a B section that is meant to contrast with the A section. Modern day song structure evolved over a period of 100+ years from these forms to what we know today.
In actuality, the simple reason why song form is so incredibly popular in today’s music is because songs are more popular than “pieces” or “compositions.” This isn’t to say one is better or worse than the other, but if the popular music of today was the music of Mozart or Schubert then we’d see very different musical structures in popular music.