Why does everyone only review individual products?

Why do you still only review individual products? Why don't more professional reviewers compare multiple similar devices on an annual or more frequent basis? Do I just think differently than most consumers? I want to know which product is the best product and why. or which products are the best for certain reasons/tasks/features. Most of the time when I decide to read reviews and watch review videos I look at reviews for as many devices as I can find. most of the reviews I read and watch don't mention any other similar products at all. Features are sometimes rated by a scale (1 to 10, or good, exellent, or bad for example) but If the same reviewer says in 2009 that this product has excellent quality and then says the same thing about another product in 2011 I don't have any way of figuring out what 2009 excellent is in comparison to 2011 excellent. and a lot of the time unless I hunt for it I don't actually know when these products were released so after watching both of these reviews I could think that both of these products are equal in quality. Is there a place on Cnet I can go to find out what products came out in the last year or two? or maybe a way to only see the newest products in my search?

I realize that this may be a lot to ask for from a company but usually when I'm making a purchase that I actually consider reading reviews, the thing I want to see the most is how the top 10 or so similar devices stack up against each other.

I'm not interested in getting answers to what is the best device that I am currently looking for but this is just an example of how specific of a product I am looking for. The particular gadget I am looking for is a behind the neck, not in ear, bluetooth headset. I want to use it with my laptop to play games and music and also to answer calls on my android phone.