Well it has to do also with the European population in Algeria. Ofc Algeria was more precious to us in terms of resources, sheer size etc, but it was also home to millions of Europeans and extremely expensive to abandon or resettle them - a bit like if all the former countries of the Israelis citizens had to take them back today if Israel were to be taken back by its native original inhabitants: a complete nightmare nobody would support and we'd rather move along and let it be a bit of a mess rather than bring the mess back home.

That was at least the feeling at the time, and we still had to do it, and it is to this day a complete mess of people brought back who don't feel French and aren't Algerians really. We'll pay for it for many decades until it finally disappear, like every subgroup that got "imported" in France and had to merge painfully since France started.

Tunisia in contrast, we really didn't care all that much, there was no cost giving it back and we lost nothing. And fast forward 70 years, we probably actually saved tons of money doing so, so we're all good.

Note that if you talk people to people, it now seems to be in the past, Algerians are proud to be Algerians, French are ashamed to have damage the country so much for so long, and we try to be good friends. I've never met an hostile Algerian, as in a recent immigrant. I've met many hostile 3rd generation immigrants from Algeria whose grandparents fled back to France, and they still have trouble accepting that uprooting. There seems to be nothing to do except wait and smile and tell them it's gonna be ok, with a glass of wine and bit of saucisson.