Why aren't hunger thirst and (the need to) sleep considered reflexes?

[RabbitWho]

A reflex is an automatic and involuntary response of a living thing to the presence of a stimulus. A reflex is usually a movement, but it can be the activation of secretion in a gland.

Is it because there is no particular stimulus? Not having eaten, drank, slept for a while is not considered a stimulus?
Is it because you have to learn what thirst is, you have to learn that drinking solves the problem?

Thank you.

 

[Simon Bridge]

A reflex is performed without conscious thought - there is no pressing conscious need to do it you just do.
Properly triggered, a reflex is something you cannot choose not to do ... where you can choose to, say, starve to death.
There is also a relatively uncomplicated cause and effect involved in a reflex.

Consider also:
do you have a "death reflex" that is triggered by the application of large quantities of high-speed lead?

 

[RabbitWho]

Ok thanks! :)