Simply put: I’m really busy.
As noted, I have a full-time day job that keeps me on the road over 150 days a year, as such, I simply only have so much time in the day. Reviews (the way I do them) take a lot of time – not only gathering data, but also writing them up. Double-checking facts and validating everything is correct.
Then there’s simply the aspect of priority. I generally try and prioritize based on what I’m hearing from readers they are most interested in. Ultimately this tends to mean that big-brands like Garmin/Polar/Timex/etc get priority, simply because that is more relevant to more people. Obviously, I review tons of devices – so it’s not limited to just those.
Next, if outside one of the major names, I look at what the device is bringing that’s exciting to the market. If it’s something I go “Damn, that’s cool!”, then it gets higher priority. Whereas, if I look at something and think “Hmm, kinda the usual.”, it gets lower priority. Then there’s the broad-appeal aspect. If the product is only offered in a single region (outside the US), it’s less likely to make it to a review. There’s just too many devices as-is already for me to review to do ones that have limited availability. Then, I look at how well products from that company have resonated with readers in the past. If I’ve done a review in the past and have seen lower views of the product and/or low comments – it tends to be an indicator of low-interest (which of course may or may not reflect the next product).
Finally, unannounced products which have time-embargo’s tend to also get priority. Meaning that if a product is destined to be released/announced on August 7th (but is previously not announced), I tend to ensure the review is ready for August 7th. If a company asks me to review a product 3 months after release, that’s of lower priority to me since information is available via so many other channels already.
I wish I could publish reviews every week of multiple products, but with the amount of time it takes, I only have one of me, and have to prioritize in some fashion.