Yeah on one hand I think they should simply be judged on their dancing, on the other hand there is an added complication in their case in that Katya's husband also works on the show.
I suspect that in a regular workplace HR might not be too happy if there was an aggrieved party on the payroll too.
This is the issue - the husband has to sit there and watch them being intimate, spending hours in each other's company etc, following them having been spotted kissing and him getting dumped over it.
Jealously must be bad enough even without evidence, in that situation surely he's got to put his foot down and say either you stop dancing with that ***** or we're splitting up? I get that pro dancers are probably used to them having physical contact with others but getting clocked outside of work is a game-changer.
As for the broader topic, I suspect it happens in most workplaces which is hardly surprising really given that people spend more time at work than they do with their partners, and the fact that we are naturally disposed to procreate - monogamy is inefficient at growing the population.