The answer these days depends upon your answer to the following questions: how fast do you need your images and how little post processing are you willing to do? If your answers are "instantaneous" and "none", then JPEG is a perfectly fine choice.
Most readers of this site, however, are looking for getting the most they can from their cameras. I like to teach photographers to turn photography into the capture of optimal data. JPEG is not optimal data. In a 24mp raw image you should have 6000 x 4000 x 14 bits worth of data, which is about 40MBs total. Typical JPEG settings these days net you about 9MBs of data (Z6), so the JPEG compression is generating, best case, only about one-quarter the data. You're not going to get that data back if you use JPEG.
There's also no compression in (most) raw data, and a good raw converter actually converts our 40MB source file to 140MBs of actual data (24mp x 16 bit RGB). In theory, we've now got 10x+ worth of data compared to the JPEG, and there are no JPEG blocks or JPEG mosquitoes (types of compression artifacts) in it. That's more what I would call optimal data.
The usual complaint I hear at this point "but it takes too long and is too difficult to deal with raw images." That might have been true 15 years ago, but today I think it's a fallacious argument. First, we have Lightroom, which effectively takes the drudgery out of raw conversion and adds a huge dose of image management, which you really should be using (you aren't just saving thousands of DSC_####.JPGs in a folder any more, are you?).
Spend a little time creating presets to your automatically-applied preferences, and then just ingest your raw files and enjoy. If you need JPEGs for Web, email, or whatever, just export those out of Lightroom. It's simple, easy, and direct. But even more interesting is that Nikon stores a JPEG basic Large image in every raw file. Recent Nikon cameras are so good that JPEG basic is darned good at all but the most extreme ISO values. So, if you need a JPEG instantly, just extract it. (Pity that Nikon doesn't make it easy, but they've been lost on the subject of workflow pretty much from the beginning.)
What? How do you do extract a JPEG? I've been telling my book customers for years, but one simple solution is the free RawPreviewExtractor (disclosure: I was the inspiration behind this program, which was created by a friend).
So the real question should be: why the heck are you still using JPEG? You've already got one in your raw file, and on Nikon cameras, that's a really good-looking JPEG. Plus you can get more pretty quickly and easily by just using the right tools at your computer. Thing is, you can't do it the other way round. If you only use JPEG, you'll never get the lost data back, ever. Never.
Okay, let me come at this a different way. Let's say that you're Disney. You're readying your latest family feature film. Today, the best over-the-air broadcast TV output is 1080i/60. The best consumer output is Blu-Ray at 1080P/30 (actually, still 1080i/60). Typical digital theatre output is 2k+, though many theaters are now 4k (7mp to 12mp depending upon which of the four definitions your theater is using). There are people talking about using 8k and even Ultra HD (16x what your HD TV can do). So here's the question: do you photograph in the lowest quality format (1080i/60) or do you use the best format available to you? Well, since you're Disney, the answer is easy: you use the best format available. Why? Because you expect to still be selling access to that film for generations to come, and you want it to be able to always be shown in its best form.
So what about you? Do you want your images to be able to be seen by future generations at their best? If your answer is yes, then you use raw. If your answer is no, what the heck did you read this far for?
