Is there any special offer from 1xbit for you to add them on your list? Any benefits you get by adding 1xbit to the list?
1xbit probably pays for the marketing in some way or the other. Especially since they are shady and have a bad reputation I assume they pay more than the better sites out there.
Another reason could be that these users use similar sources when they create their review sites. Someone else listed 1xbit, it was copied by another site reviewer, then a third...etc.