Why would a pension fund get into this? They look for assets that over the long term will create significant economic value. E.g., VCs who fund startups. But buying Bitcoin and holding it is like holding gold: the asset isn't doing anything useful while you're holding it, so you're really just making a bet about future scarcity.

If a pension fund were bullish on Bitcoin, I think they'd be much better of going long a VC fund that is investing in the space.