Have you wondered why altcoin founders create their own tokens instead of using Bitcoin which simply works better than any altcoin? For exactly the same reason Metamask will never add Bitcoin into its software. They have no financial incentive to include something decentralized like the Bitcoin blockchain. ConsenSys Software Inc. owns Metamask as well as a company Infura that provides API to Ethereum full nodes. Given that it is infeasible for common people to have their own full nodes running, ConsenSys makes money selling access to this centralized bullshit while also making money staking these useless coins. In the case of Bitcoin, however, you don't make money just by running a full node, and you can't sell anything because a full node can be spun up even on small devices like Raspberry Pi, which means if you need one, you can have one without subscription to API. Unlike Bitcoin, its full nodes aren't scarce, whereas, in Ethereum, the coin itself is abundant, but its nodes are very rare.
They actually have the incentive. Not because they don't get to directly benefit from adding BTC, doesn't mean that there isn't any incentives. Them dominating the crypto wallet category gives them a huge advantage regardless if they directly make money from BTC or not.
P.S. MetaMask is making bank from the "swap" feature of their wallet.
