BB realized why should they have a sasti copy when they can have originals in Rakhi Sawant and Arshi Khan? I mean it doesn't take rocket science to figure out that Nikki is a budget version of them and was not adding anything new to the show and hence decided to kick her
P.S: If Nikki comes back, BB will be risking the health of contestants and the crew members that's why they shouldn't bring back any evicted contestants without the quarantine period of 14 days