Maybe if it was expensive art, exotic animals or something difficult and tricky to buy and store without having specialized knowledge, yes then you'd invest in a company to buy and manage these assets.
But storing bitcoin is storing private keys... a password. Anyone can buy it and store it. Hell you can even buy it on registered exchanges, or as a security from SecondMarket's bitcoin fund.
No. These guys raised money to hire software and hardware engineers, they're looking to build a product.
Does that mean the investors aren't buying bitcoin? No, they do so, but outside the company. It's well known that there are a number of VCs (e.g. Chamath) who have bought a few million worth of bitcoins besides their investments in bitcoin companies.
I don't any evidence that many of the 'large rounds' have this business model. There are some companies that bought bitcoin, but that's for liquidity, not investments. Circle, Coinbase or exchanges all need bitcoin to sell as they're brokers/exchanges. But they didn't buy it as an investment, they could just buy bitcoin as individuals, as could investors.