Really? Remember that the ground of derogation is "motif familial impérieux" and not merely "motif familial". I can see how "motif familial impérieux" covers the situation where, for instance, my mother or brother is taken to hospital with a critical condition and I rush to go and see her or him or to look after their home if there is an urgent risk, etc... I am not clear how it would justify my traveling to see my spouse or partner because I miss them, for instance. Even if we were to give the "motif familial impérieux" a very wide definition that more or less equates it to "motif familial", what justification would that offer to a person who live on their own?
... in the same way as you are entitled to leave it, at least in the Western world. In the case of intra-EU movement, the right to leave your country to go into another EU country is even explicitly mentioned in EU legislation. I am not sure that your point is here.

... there may other reasons which are neither tourism nor work why one might travel but that is besides the point. The point is whether the restrictions on domestic travel in the decree apply to domestic travel to/from the airport in connection with inbound or outbound international travel. If you consider that they do apply, then it would mean, for instance, that a foreign national and resident would have to demonstrate that they fall in one of the exceptions listed on the attestation derogatoire before being allowed to travel to the airport to fly home and, conversely, that a French resident would have to show that they too fall in one of those exceptions to be allowed to travel from the airport to their home

If you are correct, this would mean that somebody residing abroad would not be allowed to travel to the airport to return home unless they can tick a box on the attestation derogatoire or that a French resident returning from abroad would not be allowed to travel from the airport to their place of residence unless they too can tick a box on the attestation derogatoire. Is this really your position? If not and If you accept that either of these categories can travel, then you accept that domestic and international travel are not the same and that there are derogations related to international travel which are not listed on the attestation derogatoire that would not avail for purely domestic travel.

I am not sure I follow you there. If international travel is not covered by the decree, then it means that it is allowed and, if it s allowed, then it is a necessary implicit corollary that I must be able to travel to/from the airport.