PR companies and marketing teams provide the bulk of information and test units for review. I used to occasionally write reviews internally for a leading tech review site and we were banked up with phones, cameras and more importantly, press releases. Of course, our expressed opinions on devices were entirely ours, but it would have been absolutely impossible to provide quality reviews without being sent this collateral - usually only to borrow for a few weeks in the case of test units, but very occasionally to keep
If you're a notable tech blogger, you will undoubtedly receive press releases from a myriad of sources. News channels and magazines receive the same press releases, so if you rehashed their work, you would not only be relaying 2nd hand news, but placing yourself well behind the curve.