It's damn hard to make a living as a magazine writer. That was true 15 years ago, and from what those in the industry tell me, "the money's gone out of it". As if there ever was any. The bottom line, the best new talent coming onto any magazine's staff usually find something to do within a few years that allows them to live a much better life.
So you generally have old-timers who surrendered their souls to the ad sales department many moons ago, and possibly the occasional talented young enthusiast who is on his way to bigger and better things. Then you have contract writers. For some of them, writing supplements/leverages/amplifies other activities where their rent is actually paid. They can provide real value to the magazine and to the shooting community, but what you see in print is likely overflow from something else that paid a lot more. Others are hobbyists dabbling in the publishing world to take their fun to another level.
Some are independently wealthy or otherwise retired early and mess around with writing about stuff as a way to have fun (traveling to product intros, going to shows, etc.) on someone else's dime. Simply being available to do "work" that pays maybe $7/hour when you total it up makes them a resource for editors. They don't have to be particularly good or deeply knowledgeable, as long as they produce copy that can be edited to be reasonably readable and represent the magazine reasonably well to the industry when on its business.
There are structural problems, too. A magazine depends on access to items that are not in production yet. If you don't make the manufacturers happy, you won't be on the list. Which means you'll have to wait for it to become available, and will always be last to publish your review by anywhere from a few to many months. If you're always last to market, you're not going to get the readers. And buying one of the first to market of everything you test isn't something any publisher I have heard of is up for.
I could write pages about this topic, but many others already have.
The true professional with integrity, making a living writing about a technical field, is extremely rare, and to be treasured.
