One potential reason why is that there is reportedly another team vying for Mikheyev. Both this mystery team and the Blackhawks are on Mikheyev's no-trade list, so it may come down to Mikheyev deciding which team he'd rather play for.
UPDATE: Mikheyev has reportedly waived his no-trade clause to go to the Blackhawks.
It should be noted that the Canucks don't have a second-round pick in this year's draft and neither do the Blackhawks have a fourth-round pick in this year's draft.
According to DailyFaceoff's Frank Seravalli, the two picks are from the 2027 draft. In addition, the Canucks will be retaining 15% of Mikheyev's salary in the deal. That works out to $712,500, meaning the Canucks clear $4,037,500 from their books.
Lafferty was unlikely to re-sign with the Canucks, so including his rights in the trade doesn't cost the Canucks anything. The true cost to dumping 85% of Mikheyev's $4.75 million cap hit is the second-round pick. It was a similar cost for the Detroit Red Wings to dump Jake Walman's contract on the San Jose Sharks, only the Red Wings didn't get a fourth-round pick in return.