These indices aim to replicate the market. They’re not trying to pick stocks.
There is a serious argument for saying they fail to replicate the market if they structurally exclude trillions of dollars of it.
The indices don't buy into the IPO, but a few days afterwards. That's obviously easier to bridge than 6 months. But IPO buyers are still taking a risk.
Which index are you thinking of?
Most of these indicies intend to match the largest companies on the market - going up when they do and going down when they do.
If someone doesnt want that, they can pick a different index or invest in a managed fund. Companies like vanguard also offer custom EFTs where you can exclude certian companies if you want - probably the simplest option.
But then you cant complain if they go up and you miss out.
PS: Yes, there are several cannabis ETFs if you are into that kinda thing. look into MJ, WEED, MSOS, and YOLO.
So why not just stick to the roles we agreed on when buying in?