Tesla Inc. has become the latest major corporation to make an investment in bitcoin, underscoring the increasing acceptability of the digital asset. The big question observers are asking is, why is the Elon Musk-run company doing this? Monday, electric-car maker Tesla said in a public filing that it purchased $1.5 billion of bitcoin and that it expects to begin accepting payment in the cryptocurrency for its products in the future. Bitcoin is seen as a volatile asset that is prone to sharp price volatility and Monday’s announcement by Tesla was described by some corporate finance professionals as an unnecessary addition of risk to the vehicle maker’s balance sheet in the form of currency or a commodity, depending on how you classify bitcoin.