this is not just for stocks. the potential loss of a stock is the price of the stock. that is finite. some options, even ordinary options, can generate potentially infinite losses and stock exchanges want for everyone to be able to move their stuff.
as far as you are concerned about "signals", there is something called the order book. as a normal trader you dont see this, but the stock exchange lists every position in the market and you can pay to see that. there is literally no difference between no market makers in the market and market makers having their spread quoted on top of the available market, in terms of signals. market makers just make sure that you get a good, if not fair, price for the stuff you want to move.
illiquid markets are extremely painful, especially for those companies that exist in them, because their value can be extremely misrepresented. to make an example, assume you are tesla, but you are traded on an exchange that only publishes spot once a year, in january. in august, you need to raise money at fair value and youve grown 3x since january, but nobody can give you fair price because you are quoted at januaries value.
liquidity is a good thing for every market participant.
you need to drink 5 liters of water over a period of 30 minutes to kill you potentially. thats not going to happen by accident and you will be in ridiculous amounts of pain long before you hit the lethal dose.
And yes, people do die from drinking too much water. https://en.wikipedia.org/wiki/Water_intoxication