Of course not, not necessary. At least I, cant think of one reason for that.
Usually I carry bottled water for outdoor drinking. Is it necessary to carry a water filter bottle?
It depends on your trip. If you go out for one day, I think to carry bottled water, it is ok. If you go out for several days, I think it is necessary to carry a water filter bottle. It should be convenient and portable, so you can reduce the weight of equipment and drink clean and safe water directly from river or lake with a water filter bottle.