Why did the vietnamese boat people use boats?

It was sarcasm used by the press back in 1976 & 1977 when the after effects of the evacuation was in full swing; when they said, "my gosh...their crossing the ocean in BOATS!" In reality, most were large commercial type fishing vessels that were being used. But it's an interesting subject, considering the MAYFLOWER used by the Pilgrims in 1620 was about the same size as those "boats" (90 feet long)...and it has ALWAYS been called a ship by Americans.