Because they are ill informed and willfully ignorant.
The woman was scum, yet was held up as a poster girl for all of the RC's most filthy doctrines.
A money grubbing friend of dictators and monsters, had she still been alive today she would probably rupture herself trying to simultaneously climb up the Arses of Trump, Putin and Kim Jong-un

People think that because they take her (carefuly orchestrated) goodness to heart, and swallow the myth. That's very typical of the religious.

I read Hitchen's The Missionary Position quite a while ago and it turned my disdain for her turned into a feeling requiring stronger words. I would not have wanted to be one of the people she "helped" in her missions.

I don’t think she deserves sainthood. There’s evidence she wasn’t even a good human.
Missionaries in general, I don’t agree with. They all have done damage beyond comprehension. IMHO.

Propaganda. I believe she denounced ‘JC.’ I’ll respect her for that, ‘followers’ will worship the propaganda..

I have yet to find a faith based charity that doesn't somehow require acceptance/adherence to their belief in order to receive benefits. I deplore the religious ministries that disguise their indoctrination and agenda behind good deeds.