TLDR/
TripAdvisor is of course part of Expedia/Hotels.com so it's in their interests to get good reviews so that they can then get the booking, for which they receive enormous commissions. So it is somewhat of a symbiotic relationship...
On the other hand, I have stayed at hotels (and even B&Bs) with the key card emblazoned with the TripAdvisor logo, and with me being urged to leave a review - these tend to be hotels who do the right thing seemingly all the time and are confident in what they offer.