> Who said the point of the workout was weight loss?

He is probably American. Americans are obsessed with losing weight and consider gyms as places "one goes to loose weight". Heard this over and over from relatives and others. "Gotta hit the gym after the holidays/after eating cake/etc". I tried telling some of them how unproductive it is to run on the treadmill for 2 hours then eat a large BigMac but it just doesn't register.

Weight and health are not necessarily strictly and linearly related. One can be thin as a stick figure and be very sick or can be overweight and relatively healthy. Why should one go to the gym? There are many reasons, feel better, get stronger, get more nimble, improve dexterity, improve mobility, meet people, and yes loose weight too but is just one of the reasons.