As far as I can tell, there have been "Best Answer Contests" from the first quarter of 5777 (here) through the second quarter of 5780 (here). As evidenced by the comments, nominations and votes at the last one, it appears that participation was way down. Since then, there have been no "Best Answer Contests".
Why have they ceased, and was there some sort of formal discussion that caused that?
Would people be interested in having one for the first quarter of 5781 (only slightly late)? I'd be happy to offer the bounty from my rep, if someone else can do the posting (just because my schedule and MY access is too unpredictable these days).