It's an art and a science. It has advantages and drawbacks. It adds color, flavor and texture to a journey but it can also impose additional hardships.
My bike, with all its storage space, is well suited to moto-camping; my system (as shown below) is to secure my sleeping bag and tent to the rack on my topcase using a bungee net with hooks. Simple, but it works.
Then I put all my clothes and other personal items in one side case, an inflatable air mattress in the other side case and all my miscellaneous bulky riding gear, maps, tools etc. in the topcase.
The primary benefit to moto-camping is that it's usually very cheap. This really helps to stretch the travel budget.
A secondary positive aspect is that it introduces an element of adventure. You feel just a little bit more intrepid when you sleep in a tent, a tad more self-deterministic, marginally (albeit temporarily) more free, less connected to society, less encumbered by the constraints of civilization. There is nothing quite like enjoying a campfire under the stars out in some remote area all by yourself.
There are, of course, also some significant minuses. First of all, it takes much longer to settle down for the night and much longer to get going again in the morning; you have to work this into the daily schedule. Whereas checking into a motel is typically quick and easy, setting up camp takes time and effort.
Another problem is that you leave yourself vulnerable to the whims of the weather. If it's cold and rainy, camping might sound less appealing than a real bed indoors, particularly if you've been riding all day.
And lastly, there are no hot showers, no flushing toilets, no pizza delivered to your door. Of course, that's the whole point. But if you've just banged out 500 miles and you're tired, stiff, sore and cranky you might be in the mood to take it easy.
The picture above shows my improvised campsite on a perfect late afternoon in 2006: I got there in plenty of time to set up my tent before it got dark, it was a lovely day for being outdoors and the ride that brought me to that spot was not excessively arduous.
My own guideline for moto-camping is to limit it to no more than one-third of a trip. Of the remaining two thirds, those nights should be divided between ordinary motels (for economy) and more offbeat lodging -- such as art hostels, bed & breakfasts, tree house cottages, spa resorts or crashing out on a friend's sofa. While it's tempting to become over-reliant on hotels, I have often looked back to realize that some of my most memorable moments on the road were at the more unusual and exotic overnight stops.