"Speculation"=taking advantage of different price differentials. But in speculation, the only way you can ever make money is to sell. Period. No amount of silver or gold in the world is worth anything if you don't sell. Nor will it pay pay a dime of dividends or ever split. So, sure, you can sell silver because of inflation, and you can buy and sell oil. But at some point, you have to BUY BACK or you can't do it again. Not true with an investment.
I also own a business which generates a respectable ROI, so I get your point.
Precious metals are a good hedge against drops in value, though. They’re an excellent place to park savings, because Federal Reserve Notes are going to devalue now. Converting a doomed commodity (dollars) into a stable commodity is a smart move, even if you don’t want to technically define it as investment.