Notso - just like everything else in life, there are cheap sites and expensive sites; good sites and bad sites.
If you join the Caravan Club, you can use their CL (Certificated Location) sites. These are great - just 5 vans per site and often very basic. There aren't the luxuries of a big site (eg washing machines etc) and there are often no loos, but many have hook-up.
The real benefit is that there is so little traffic, the kids are very safe to wander around and enjoy the sort of freedom they wouldn't on a big site with cars coming and going all the time.
Also, they're much cheaper - I think they start from around £6 per night. We're going to a CL for our main holiday this year - it has hook-up but no other facilities - and I know we'll have a great time for very little expense.
If you like this kind of caravanning (basic!), you'll soon recoup the cost of joining the Caravan Club. All CLs are listed in the handbook they send you, and I think they're trying to get more CL info on their website too, alongside the big sites already on there.
Finally, if you have Google Earth on your computer, you can put the CL's postcode in and have a snoop online to see if you like the look of it before you book.
Big sites are more expensive, especially in school holidays, but there are great alternatives available. We love CLs, and so do our kids. Give it a try, and don't let the anti-caravan brigade put you off!