Baby shower

Do you guys think it's rude to not invite kids to a baby shower ?? 
I got my friends invite recently and it says no kids. I just think it's rude becus almost all of our friends have kids. 
I could understand a bridal shower or wedding or even funeral something a little more "formal" but a baby shower !? 
Should I tell my friend I'm not going becus I have my son ? I'm not gonna get a babysitter just to go to her shower.