The founding fathers felt it very important for the constitution to be amended because as time progresses, the world and society changes and goes through processes of evolution, therefore the needs of the times change. People back then didn't have smartphones, internet, etc... so the rights / rules for freedom of speech, online businesses, respect online, etc... didn't exist. Whereas nowadays we are living in the beginning of the technological era, now we have many more and many different problems, than the ones that existed in the past.
This factor affects that idea, and also, with overpopulation in the world, the human mass increases and consumption, rises.
----> The specific answer is that, different times, different needs. Society changes, and different problems rise.
