It's called "the gateway drug" for many reasons, one of which, is that it opens your mind to the realization that what we see is not always what we get.
That's it! That's really all it's good for, which is not to say that it is all bad, but too much of a good thing can be a bad thing.
I heard a description recently about weed:
Think of it like this: You're a scientist, and you look through a microscope. All of a sudden you see a world, or view, that was previously not open to you. The object of your attention has a whole new dimension. It would then, be a mistake, for the scientist to go around everyday with a microscope strapped to his eye(s), and expect to get the same depth of understanding of all the things that he/she encounters. That's not to say that there wouldn't be knowledge to gain, but this would be the rabbit hole that swallows us all. That's where we abuse the gift of the tool.
Weed, psychedelics, etc. are tools. Some beings get so good at their art, that they no longer need tools to create it.