We didn't want a castle or any kind of magical princess days for our wedding
We wanted somewhere that 70-100 friends and family could sit down and enjoy something to eat and drink, then have a dance
I've never been to a wedding that wasn't babes in arms only for anyone but immediate family.
If you have a guest list of 70-100 then if most couples there have at LEAST one kid, then you're now looking at somewhere that can seat another 40 plus people. That's a lot
Seating for over 100 people rules out a significant proportion of wedding venues. Not fancy schmancy ones but anywhere that can accommodate that many people seated. Even if it's a buffet, you still can't have fewer seats than people. So you need table space for your guests to have something to eat
To accommodate families, you'd have to uninvite loads of your guests.
Like I said, I can't think of any wedding I've been to where it wasn't a predominantly child free wedding. In London (or I imagine most major towns and cities), you're looking at mega bucks for a conference style room that can seat so many people, because fire regs mean they're strict on numbers
Most folk I don't know don't want to and can't afford a grand ballroom just to accommodate everyone's kids.