Why is "freeze your nan" a more politically tenable tough decision than legalising cannabis?

We're pinching pennies to a point that we have to make "tough decisions" like reducing winter fuel, child benefit cap, and benefits reductions.

These are all in spirit "taking things away" from people (even if you don't agree with it, it has been received like that by the general public).

Where as legalising in a similar manner to Canada is in spirit about giving people more freedom and could bring in a steady revenue through taxation and related economic activities. Maybe not tens of billions, but at least enough to at least partially fund some public things while freeing up police resources.

What is it about the politics of this country that makes the politically more justifiable for the former to take place? That's not a rhetorical question, I'm curious to see what your theories are on this.