Jesus was right up front with them.
John 6:26-27
"Jesus answered them and said, Verily, verily,
I say unto you, Ye seek me, not because ye saw
the miracles, but because ye did eat of the
loaves, and were filled.
Labour not for the meat which perisheth, but
for that meat which endureth unto everlasting
life, which the Son of man shall give unto you:
for him hath God the Father sealed."

People are taken with their present physical
needs with complete disregard of the future.