Except drinking all the time also has proven drawbacks. In proffessional sports, drinking too much plain water is known to be detrimental to performance.

You do not sweat nearly enough to warrant the multiple glasses of water the average school teacher makes kids drink in PE nowadays. Even though you do get thirsty.

What your body actually needs, are the salts and other minerals you just sweated out, which was the whole point that created Gatorade.

Also a lot of the research that claims thirst to be "too late" in telling you when to drink, is funded by companies that sell bottled water.