Because the majority isn't always right.
They don't want it
They don't want themselves nor their loved ones involved with it.
The simple answer is this: The vast majority of the people voting to keep it illegal do not suffer from the diseases that it could cure or help treat.
There are many potential answers to that. Peace and stability is what most people want. At this point the majority want to stay in the United Kingdom.
They did not want to bail the northerners out.
The unionist or loyalist people, the majority of whom are protestants.
As of 2013, the majority of Democrats in Congress support marriage equality. The majority of Republicans oppose it.
oppose - mean support - needed it
It does not always reflect the preference of the majority of the public.
The great majority simply want a fair government that will be honest with them.
He advised people in Moscow to oppose the coup.
Democracy works by majority rule this means that citizens agree that they will abide by what most people want.