Is that not just because these French guys don't have long term girlfriends? We know who Llodra's wife is, we know who Simon's partner is(even if she doesn't attend many tournaments)
yes you're right, that's probably their main difference.
But still I also have the impression that one doesn't see Simon's wife very often, Mathieu is also married and now has a baby and I saw his wife only once I think even though he had a lot of dramatic matches and she could have been in the public, never seen any Benneteau's girlfriend or wife either, Grosjean I hardly remember either although he had babies quite early, I think
... and it seems to me that for some other players we also could see their short-term relations more often.
Also we hardly speak of French players' wives or girlfriends on French TV, it seems to me that French players have decided to hide these relations more secretly.