When you just can't (or don't want to) change lenses, sometimes you're willing to make compromises for a lot of versatility in focal length. While superzoom lenses have long been chided as being consumer grade and below par for "real" photographic use, the major manufacturers' most recent designs are surprisingly good. For example, Nikon's 18-300 DX-only lens actually has quite respectable performance, all things considered. This lens is no different. Yes, the maximum aperture is relatively small, but that also means the overall size & weight of the lens is kept to a minimum. That means that as a travel lens, this really fits the bill quite well. You can do a huge variety of shots with it (especially outdoors), and it doesn't take up too much space in your bag or weigh you down too much. This particular lens also has very good performance on the telephoto end, which has typically been a weak point in superzoom designs of the past.

So until the optical engineers discover a way to make a full-frame 14-600mm f/2 that's the size of a soda can, weighs 6 oz, and costs less than $800, you have to choose the things that are most important to you. If you don't have a film crew to schlep your gear around or a huge production budget for the fastest prime lenses, then this is a great compromise and will give you a large range of options for your next trip.