Wow, you are right. Life would be a black joyless void of suffering if we drank water when we were thirsty. (OK, reflex sarcasm satisfied).
We aren't talking about "now and then" we are talking about habitual daily consumption of empty calories from sweetened drinks.
Apple pie is +/- 350 calories per slice. Depends on how big the slice is of course. Add a scoop of ice cream and you are near 600 calories. An occasional piece of pie is a fine thing. A slice with every meal, day in, day out not so good.
I'm thinking of one of my co-workers who drank 2 or 3 mid-sized bottles of soda (20 oz?) during the workday plus a tall cup (32 oz?) with lunch. He was packing in about 1000 calories just in soft drinks every day. He was asked (not by me, I've learned better) why he didn't drink water. He acted all hurt and defensive, like he was being criticized for his choices, and as though his obesity was somehow his fault. He liked sugary drinks and he felt entitled to drink them. It just didn't occur to him that there was any negative consequences to his choices, or that if there were any it would be his fault.