I think it completely depends on the couple, and even though I am a mother, I have no issues with it whatsoever.
For my own wedding, I would have children there, but only close family members (my son, younger cousins etc.) not someone from my work's child for example. I have seen weddings where the bride and groom provide 'goodie bags' at the reception for children for during the speeches which are age appropriate - colouring books etc. I've also seen ones who will give children disposable cameras and a list with "take a picture of: the bride in her dress/ the bride and groom kissing etc." to make the children feel included and more likely to do that than run around.
I also know one couple who put a magic show on during the pictures and start of reception/speeches for the children to go to so they wouldn't get bored.
However, I've also been to two weddings without my son (three with), and it might sound selfish, but I relaxed more during the two without. During the ones where he was there, I constantly worried if he would act up, would he get dinner in time, would there be accidents, where was he etc. and I didn't get to sit and appreciate the day properly. In the two without I could relax a bit more and appreciate what it meant for the couple, as my mind wasn't on one hundered other things.
Some parents see it as a nice break, some don't want to leave their kids. You cannot please everyone, and, especially with a wedding, the bride and groom should do it the way they want it. If people throw a fit/don't come, then so be it.
EDIT: Just thought I'd add, my son was 11 months old at all three of those weddings, hence the needing to stick to schedule. Now as a toddler he wouldn't be as bad in terms of routine and it would be easier.