Does the nature of "Market Makers" lean the profession towards the public good side of the public-private spectrum?

The benefits that registered market makers (MMs), or equivalent volatility suppliers, consign to the efficiency of the equity market is a concept that deserves careful consideration. MMs provide valuable liquidity to the stock exchange, and in doing so increase the functionality of the market. A primary aspect of MMs is that they are (for the most part) not profit-making entities, MMs are not speculating on the price of a stock, nor are they inclined to justify their actions with thoughtful due diligence. It is clear that a world without market makers would be a world with limited liquidity; the price formation of a particular security would be feeble, susceptible to the daily fluctuations in the proclivity of an individual to sell their securities to a buyer (or vice versa). This promotes the idea that Market Makers serve, in some sense, as a public good as the positive externalities (efficient and highly liquid markets) that result from their actions seem to surpass the negative ones.

Since the efficiency of the market depends on MMs, there is justified support for regulation via policy. One example of this is the 2019 Lead Market Maker (LMM) incentive program, a program the CBOE deployed to incentivize Market Makers to meet liquidity and market quality metrics. If Market Makers are rewarded for their ability to supply efficient markets, does that remove them from the discussion of being a public good? I’d surmise no; incentives are used often to reform and ensure the proficient caliber of public goods. Regulating Market Makers is a way that policy can ensure highly efficient markets, though sometimes this regulation has not always yielded the results policy makers would hope for. Market Makers are non-rival in consumption (one person’s trading of a security via market maker assistance does not detract from the next person’s predilection to do so) and non-excludable (anyone who trades almost any stock is subjecting themselves to an inescapable realm of MMs.). This analysis leads me to believe that MMs are more towards the public good side of the public-private spectrum than they are towards the private good side.