You know, I don't think any of the cars I've owned have coolant level sensors. They all have had coolant temperature sensors though - which I admit doesn't work exactly the same way, as I can think of some ways that an engine could destroy itself where a coolant temp sensor wouldn't indicate anything is wrong (if it were run dry, for example - but you'd have to almost try to get an engine in that state).
As cars age, the likelihood of leaking coolant goes up. Dried cracked hoses have always been a problem, but in cars made in the last 30 or so years, all the reservoirs are plastic and could crack as well.
Coolant level sensors are a very good thing to have. It saved my butt once. Big warning triangle light in dash instructing me to pull over immediately or risk engine damage. That was on my 2009 S80 though, when a repair shop dislodged a coolant hose.
The thing is, car manufacturers don't really care as long as the car makes it through the warranty period. After that it is on you. That's why we se so much **** these days, like 10k mile recommended oil change intervals (no, synthetic oil is not "good enough" to protect your engine for 10k miles) and so called "sealed" automatic transmissions without a dipstick or convenient ports to replace or flush the transmission fluid. There is no such thing as a "lifetime transmission fluid".
I mean, sure, if people expect to buy new cars and dispose of them after 5-10 years this is fine, but if not these types of things are
really bad ideas.
My S90 has a 10k mile recommended oil change interval. I do it every 5k miles. You can't trust that ****.
I'll also try to figure out how to flush the transmission despite it being "sealed" by ~80k miles as is best practice, even through the manual has no recommended maintenance interval for transmission fluid.
Not doing so is foolish if you want your car to last.