Fish tank water tastes horrible. When you have a fish bowl it’s easy to scoop out the fish and then just carry the bowl over to the sink or toilet to dump it out. If you need to empty a tank you have to do something else. You can get a cup and scoop out the water for the next hour or be a smarty pants that know how to siphon things… except give it a second for the water to come out before giving up and putting the hose back in your mouth.