It's because the actual institutional language used the term, so marginalized groups often continue to bring to the forefront the language the government employed (or still employs, in the case of Indian) as a way to combat the post-90s "liberal mosaic/colourblind" narrative that permeates Canadian society. Canada exists in this ahistorical cultural vortex where slavery was an American problem (they stress that the Underground Railroad led to here, but ignore that at the exact same time Canadians had their own slaves and it was border laws that "freed" slaves coming North, not an anti-slavery sentiment, and rarely teach about Canadian slavery at all) and work camps were a British problem (don't look at what Canada did to Asian immigrants please) and residential schools are only recently even talked about at all.
It's about rejecting this false ideal Canada has that it "solved racism" or whatever because it was always "more progressive" than America (please ignore that the country was founded by Orange Order racists, that the RCMP exists to wage war on the Indigenous population, and that the KKK chapters here flourished without scrutiny).
Anyway, that particular word is used a lot when addressing Canadian foundational myths, which are built on the idea of the railway (and especially the Canadian Pacific Railway) as this great nation-building project that allowed Confederation. What that myth most often ignores is the work camps of sino-immigrants, the violent occupation of the West and the consolidation of the industrial bourgeoisie as the ruling class as they ousted the old feudal order.
It's a term used less in a reclamatory way by Asian academics and activists, and more in a way that forces acknowledgement of the racist legislative bodies of the country. There's a lot to be said about the way pejoratives can be used in different contexts, but, especially online where you can't know anything about the person on the other end, it's usually best to avoid them altogether so as not to cause unintentional hurt, for which I apologize.
Yeah that's what Canada wants people to think, but unfortunately: https://www.cbc.ca/radio/sunday/the-sunday-magazine-for-november-22-2020-1.5807350/the-rise-of-the-ku-klux-klan-in-canada-and-why-its-lasting-impact-still-matters-1.5807353
"In just a year, the group became the largest and the fastest growing social organization in the country"
""You had rallies where you had five, 10, 15, 20,000 people who would show up at these Klan meetings in places like Kingston and Belleville, London, Hamilton," said Bartley."