I'm distinguishing it from investments that pay a dividend or interest coupon at time of purchase, or which have a commodity value independent of price (eg gold and oil are commodities that you can speculate in or take delivery of for actual consumption).

You might well get rich from speculating in bitcoin, but if if doesn't pan out then your assets could end up having no value whatsoever - you won't even be able to burn them to keep warm during the zombie apocalypse ;)

I'm not trying to comment on the viability of BTC here, just pointing out that it not the same as many other asset classes.