Isn't "olive oil butter" basically exactly what margarine is? It can also be made with other vegetable oils of course.

I don't prefer it over butter although this is largely a matter of taste, but more importantly IMO, even if it was touted as a healthy alternative to butter in the 70s-80s, today margarine has been shown not to really be better after all. It's not used much anymore by people less than 50 or so, in France.

I think modern margarine is probably better as it doesn't contain much transfats anymore, but in France the damage to its reputation has been done already.

I live in Belgium though and people still use margarine here, but as far as I can't tell it's mostly because they just call everything "butter" and don't know the difference between margarine or butter.