Well you could say the same about them only showing some PS4 logo then. Although showing the PS4 or XB1 version of the game is probably a better idea than showing the Switch version. They cant really make different commercials for all the different versions. That would be silly. Nintendo should step up and start hyping some third parties instead of informing us of third party games in the tone you would inform people to remember their flu shots.
You summed up the attitude of third parties pretty well. Nintendo is supposed to do the work for third parties to make third parties make more money whereas on other consoles third parties know no restraints to do the work themselves.
There would be nothing silly about making a dedicated Switch commercial. A Switch version adds the value of portability to any game by default, so that's what justifies the effort of making a special commercial.
Nintendo won't care if the big third parties don't want to make money on Switch because Nintendo makes big bucks without them. Another factor is that the absence/reluctance of the big third parties puts more of the spotlight on smaller third parties, including indies, who are happy about less competition and laugh all the way to the bank.