You need them. I'll just confirm your gut. It all depends though on how much the wet ground bothers you. I have a dog so it bothers me a lot. You can grade so waters runs off but generally there are still issues.

I've built 2 houses. I've installed a lot of french drains after the fact. I'm getting ready to install some more.....

You should realize that sod helps dry the soil and winter is the worst for staying soggy. If your neighbor had standing water - that is pretty bad. I don't have standing water and you probably won't either but that doesn't mean you won't have soggy soil and wish that it wasn't so....

I put these in one new home with similar ground conditions--flat with high clay soil that left rainwater pooling for weeks on nearby properties. A relatively easy job when the home is being built and Cats have free rein; messy when you're working around an occupied home and trying to preserve yards, drives and plantings.