Upon listening to his officers make some good points, Alexander initially considered staying at the foot of the hill for the night.
But then soon thought better of it as he found numerous problems with it.
For one- say nothing of staying outside basically naked in the cold night, without a tent or some kind of shelter, the spring night was not nearly as warm as his men were making them out to be.
If he wanted his men to lay on the cold ground with perhaps their cloak as the bed, it was going to be torture.
Two- such open grounds were a prime invitation for the Heeats to launch night raids. They did not even have time to set up a ditch.
Hence if Alexander followed his officers' advice, he would have half of his men staying awake the entire night on guard duty and the other half catching a cold by the next day, and all of them being very hungry and angry by the end of it.