Even I make enough money to cover my travel costs and show a profit. Plus the IRS allows losses some times; I think the rule is every 2 or 3 years out of 5 should show profit to not be considered a hobby but I'm not really useful for tax advice.

As for why they review the same thing over and over again, most likely because they like actually consuming the product so they keep doing so. And if those are the flights you're on and you feel compelled to write a trip report for every trip then those are the flights you'll review.

I find it skews the quality of the report when there is less evidence of comparative consumption by the reviewer; how does someone know product A is better than B, C, D & E if they've never tried the others?? Some are better about that than others. But that's part of why I go out of my way to fly different carriers whenever possible.