I can give you three different reasons:
1) The Illitch's and Fedorov had a falling out after the very tenuous 1998 negotiations where Fedorov was paid $28M for a single season (!!!). He originally held out and then, signed an offer sheet with Carolina. To disparage the Wings to let him go (this was like MLB, pre salary cap), they gave him a $14M signing bonus AND a $12M bonus if the team made the Conference Finals specifically in 1998. Carolina wasn't good at the time and knew they wouldn't make it, but Detroit was. Mike Illitch paid it anyways coming off the Cup win and Fedorov only played 21 games plus the playoffs (where the Wings won the Cup again). When Fedorov was signed by Anaheim after the contract was up, Illitch didn't even talk to him on the way out because of how that went.
(Crazy enough, this is still the largest single season payout to any NHL player in league history).
2) Sergei has been a prominent head coach and GM in the KHL for a significant time. The seasons run congruent, so it hasn't been good timing to get him over here to do the ceremonies. Plus, with the issues with Russia, a lot of players have been hesitant to come back to the States or vice versa.
3) Red Wings have had pretty high standards for retired jerseys. Allegedly, Fedorov did not meet the Illitch criteria (allegedly, it was the years, Fedorov played 13 years with the Red Wings).